I suppose you were longeing her in a halter. That doesn't allow you to have any control over your horse when he really wants to go somewhere.
You need, ESPECIALLY if you have no longe area, a bridle, a longe line in good condition (cotton web - no nylon ones - impossible to hang onto and will burn your hands even thru gloves). You need a longe whip, and gloves, really good gloves that are thick and fit your hands very well, and sensible work boots.
A good idea would be to get a snaffle bit - a ring bit - not a western snaffle type bit with shanks. You want to have something things can't get caught on - so shank bits aren't good for longeing. Also, believe it or not you don't want to have a lot of leverage when you are longeing, because you're pulling to one side, rather than back (as you would when you're in a saddle riding).
They can be bought very cheaply. They aren't costly.
Some people, what they do is if they don't have a lot of money, they will string up some electric fence around the area they want to longe. It can be quite cheap to buy some electric tape and a few fiberglass rods, they're portable and can be used later when you are just trying to keep the horses off overgrazed areas.
But in general, I don't care for that as some horses will run right through that.
If you cannot put together a STURDY fence to longe your horse in, then you need to have some control of the horse.
Now, I know many people think 'the horse won' and 'now she is the boss' - I urge you to not worry about that. It really isn't like that. You just don't want running back to the horses to turn into a habit.
Now, if you can't make a longeing area with a gate you can close, you can do one of a couple things.
One is to longe near the barn and the other horse, so the horse doesn't have that long distance to get excited over. Horses tend to be quieter and calmer when other horses are close by. They generally don't run off.
However, you may still have problems with the horse trying to turn toward the other horses, follow them, or just simply stop when being made to go away from the other horses.
I've had some very rough horses to longe with no area set up to longe them in. What I do is first, put on some very good gloves, very good strong work boots that fit very well and lace up tight, and yeah, I put on a helmet.
Keep in mind, you ALWAYS know where on the longeing circle the horse is going to try and go back to the other horses. He's going to run toward the gate, toward the other horses, it's always the same thing. You KNOW where he's going to try it. They nearly always try it in exactly the same place on the circle. BEFORE YOU GET TO THAT POINT, start bending his neck in toward you and getting his eye on you. DON'T WAIT TIL HE'S HEADING STRAIGHT FOR THE OTHER HORSES - START BEFORE HE GETS TO THAT POINT.
Because for one thing, no matter what happens, I am not going to let go. I don't want them to get a habit of running off. Not only that, I would be worried about them getting hurt right just that one time. It has happened. I would not want one of mine running loose down the driveway toward the highway.
But to do that, I am going to make sure I have something in my favor. That is, I have the longe line on the BIT, NOT THE HALTER. There is NO WAY IN THIS SWEET WORLD ANYONE CAN HOLD ON TO A 500-1500 lb HORSE when it has a halter on it and it wants to go somewhere and gets its neck straight.
Now a key thing is when you are trying to hold onto a horse, NEVER wrap or even turn or flip, the longe line around your hand, arm, any part of you. ALWAYS have it arranged that you can drop it and it will fall totally free of you.
The old horseman's home is FULL of people who have no use of one hand, who have torn out their shoulder, who have torn out their elbow, or lost a thumb or finger, because they wrapped something round their hand. EVEN IF THE LONGE LINE END IS IN BIG LOOPS - DO NOT EVER PUT EVEN THOSE BIG LOOPS ROUND YOUR HAND...NO MATTER HOW LOOSE. PUT YOUR HAND AROUND THE LOOPS, NOT THE OTHER WAY AROUND.
What happens if, the horse takes off, he is going to drag all one hundred and - well - all my weight, on his MOUTH. Yeah. Not pretty. It's going to hurt his mouth. But it's going to be brief, and he won't do it again.
These habits are dangerous, for the horse, more than anyone else. If a horse gets out on the road he can kill himself and anyone who is in the car he hits.
And frankly, I ain't got enough insurance to cover how many dollars I'd get sued for if that happened. That and I like my horses and I'd rather they did not die or get maimed, or kill anyone else.
But if anyone else is around it's dangerous for them and it ain't too keen for the handler either.
So.
First, I am going to try and catch him at it before he gets going. When he STARTS to take off, I am going to give him a fifteen inch smile and bend his neck around, and he is going to know that this is not a behavior I like.
And I am NOT going to allow him to stop and rest then. That's a reward. He is going to work, and keep working. I'm not going to brutalize him, I'm not going to make him tear around so fast he hurts himself, but he is going to work.
WHY? Well mostly because he obviously needs it. He's probably got a ton of accumulated energy and isn't getting enough exercise.
I am not going to let go - well - I am going to be reading what is going on, I may still let go if the horse has completely lost its head and is running toward a semi. But - most of the time, I am not going to let go, even if I get knocked over, even if I get drug, even if I am being taken for a Nantucket Sleigh Ride. I can put the longe line around my butt to help enable me to hang onto it, and sit down and the horse can drag me for as long as he wants. DURING that time I am going to try very hard to pull his neck around to the side so he does not have his neck straight forward. That can help stop the horse. I am also going to try and guage how NUTS the horse is. Some fairly reasonable horses go insane when they are in that situation, I'd be ready to let go of the longe line if it looked like holding him wasn't going to work or I was going to get hurt.
There's an amount of experience that comes into this. If you are a novice, you might need to not go to any of the lengths other people might go to.
If you're a novice, it might be hard for you to catch the right moment and turn him before he starts running.
Most of them will stop pretty quick.
The REAL TRICK, however, is to not let it get to this point. When you see the horse start to run, TURN HIS NECK, BEND HIS NECK.
A horse with his neck straight out in front of him is a horse that can do whatever he wants, where ever he wants, however fast he wants. To control your horse you need to turn his neck.
Here you can see a pretty lazy horse, but whenever the horse gets his neck too straight or starts looking out to the outside of the circle, the longer turns his head in toward her - and when he starts cantering, he tries to get strong, but she TURNS HIS HEAD TOWARD HER - you can also see every time the horse starts looking 'over there' where the horses are, she turns his head back to her.