I've glanced over your posts again Naturegirl, and I can tell you've caught the bug for chickens and guineas. Welcome to the insanity! Your pen/coop setup is just fine for chickens, but as you already know, it won't keep Miss Guinea in, LOL. Guineas are strong flyers and if spooked, they'll go over in a second. The problem is, they have no idea how to get back IN. LOL. They aren't the smartest fowl in the yard, but what they lack in I.Q., they make up for in quirky, entertaining behavior (if you like guineas).

. Plus, they naturally roost in trees unless taught otherwise. So you need to teach her "otherwise".
Guineas need about six weeks penned up to program them to know where "home" is. I'm not sure, but it sounds like she knows your place is home, but she doesn't know to come back to it every night. Lock her up for about 3 or 4 weeks (or more - - six is the recommended minimum, but
sometimes less time will work).
Since you're "hooked" (we all understand) you might want to consider covering your large pen area since it won't be long before you want more guineas.
. How tall is your large fenced area?
You can rig up anything - large tarps sort of "tented" over the fence, like a circus tent sort of. Or you can run chicken wire underneath tarps to keep rain off and provide some shade. You don't have to cover the entire pen, just part of it. Then close that covered part in so you can rest easy, and she'll be safe at night from nocturnal predators.
Then start the coop training. Keep her penned for some weeks and every night at dusk, go out and give her a treat (white millet = cheap, mealworms = expensive, etc.) and say the same thing every time you give her a treat. You can use bells or whistles if you want; it doesn't matter. She'll learn to come running when she hears the signal. Also, she'll learn that the pen/coop is where she roosts every night. That's really what you're trying to teach her.
Consider getting more guineas. Guineas are flock oriented in the extreme and while chickens
help, nothing takes the place of their own kind. People recommend a different number, but if you have room for 10, consider it. Miss Guinea will be a lot happier, and you'll get lots of breakfast eggs - not to mention a lot of fertile eggs to hatch. But beware, guineas can become a big part of your every day by choice. Like chickens, they can be addicting. You can let them out during the day and then pen them at night. You can spend a lot of money on a coop and run, or you can do it inexpensively if you don't mind less-than-beautiful housing. The guineas won't care one bit, but if you can afford it make it beautiful
. I add a little to my pens and coops every spring.
Guineas are very weather tolerant, but they need to be able to get out of the wind and rain, especially in a cold northern climate like Ontario. Building a large, insulated coop will be a good idea for all your fowl. THEN, you can consider TWO coops - one for guineas, one for chickens.
Oh and it goes on from there LOL.