sounds like a normal 4 month old puppy...they don't speak English, so you wouldn't expect her to know what "come" means. Whatever you do, do NOT EVER scold or punish her when she comes to you, no matter how many times you've called or how long it takes (or how mad you are!). You will only teach her that coming gets her in trouble. Dogs live in the moment, praise or correction must be instant or they will attach your response to the wrong action. I use clicker training, which, once the dog understands what the clicker means, allows you to "reward" the exact behavior you want. LIke any other reward system, once the dog knows what you want, you needn't have the clicker at all times...I just use it to teach a new behavior, then "fade" it out.
Your puppy needs to learn that all good things come from you. Attention, food, going outside, getting toys or treats, walks, everything. I suggest using NILIF - Nothing In Life Is Free. First, you have to pick up all the toys, close all the doors, put away all the food bowls. If your little charmer wants to play, she has to sit. Then she gets her toy. Then you teach her to give the toy back after a few minutes by offering a treat or another toy, telling her "give" , and AFTER she gives you the first toy, she gets the other one, or the treat. When you decide playtime is over, you go get the toy from her (this time, use a treat to reward her for giving up the toy), and put the toy away where she can't get it. Then take her out or do something else with her (maybe a training session). Teach her to come in the house first, before you try it outside.
Before she goes out, or gets petted, or gets her food, or ANYTHING she wants, she has to give you something. She has to sit, or lie down, or come, or stay, or fetch, or play dead, or whatever - but nothing in life is free, she has to work for everything she gets. This is not forever, just to teach her that you are a very important person who controls all the good things in life. When I get a new puppy, at meal times, I hold the dish and hand feed one kibble at a time, asking the pup to sit, or down, or "watch me", or stay, depending on age and level of training. I am the supplier and controller of the food. I never leave food down all the time. If you do that, you are not controlling the food, and therefore are less important to the dog.
You don't want to be a stern and scolding despot, you want to be a benevolent dictator. Just like a toddler who doesn't have manners or self control or understanding of rules, you have to teach your pup with firm, fair consistency. You will get a lot farther, a lot better results if you use more praise than scolding. Praise small steps toward the behavior you want. For instance, if you call the dog and she turns to look at you, tell her "good girl". Show her a treat or toy, and call her again if necessary, Praise and reward when she comes toward you. Have a party when she arrives.
You don't say whether she got any socailization or training or was taught basic manners in her former home, and you don't say how long you've had her. I would also recommend crate training her. It will give her a safe place to be when she can't be watched, and it is one more aspect of her life that you can control. It will also give her a "den" to hang out in.
Don't wait to start her education. Be patient, realize that she doesn't have a clue what you want, and she has no reason to think that what you want is more important than what she wants. I start training my pups the day they come home (8 weeks old). Like any young thing, attention span is limited, but each thing she learns will be a foundation for the next thing. She is learning how to learn from you, and each thing will be just a tiny bit easier to teach than the last one was. I would not teach too many things in one lesson - I might spend ten or fifteen minutes teaching sit and down. then go do something else, and later in the day spend ten or fifteen minutes teaching sit and stand. Teach come at every opportunity!
THere is far too much to put in one post, but do your homework, read a lot and do what makes sense to you. Build a good trusting relationship with your dog and you will be able to do anything with her, in partnership. If there's a local St Bernard breed club around, contact them. Go to the American Kennel Club website (AKC) and click on your breed and you should find a listing of local clubs. If you can take her to obedience classes, do it as soon as possible. She is going to be very big and needs to learn to go places and be around people and other dogs without being afraid or defensive. Even if she will spend most of her life on your property, she will need to go to the vet and you will probably have company at times...teach her NOW that new experiences are fun, or you may well have a real problem later. You may notice from my tag line that I have Newfoundlands...trust me when I say - SOCIALIZE HER!!!
Besides, it's a blast to take your big dog places. I thoroughly enjoy being able to have my dogs' company while I'm out and about. They go with me to the feed store (they can go in), and the hardware store (Lowe's is dog friendly), we go to a local park sometimes just for somewhere different to go...we drive into town and go for walks so the dogs learn that cars won't attack them and that buildings and other walkers don't hurt.
Above all, enjoy your dog. Training should be fun for you both. And remember, the dog doesn't know the difference between learning sit and come or learning a "trick" like shake hands or play dead. It should all be just as enjoyable for you both. Good luck!
