First of all you should see with a vet if she doesn't have a problem that would harm her and make her buck (saddle too tight or less muscles than before).
Then, there are several options to make a horse stop it, put movement ahead, it will be a lot harder for him to buck if he's in action.
Don't stop him, he'll understand that when he does it you stop. Keep asking him by putting pressure until he gives in to your request and then directly stop the pressure and reward him.
You can also put him a small circle, it will be harder for him to buck or even try to ask to trot outside of the arena somewhere that climbs.
You need to act like it doesn't bother you but always try to pull his head up.
I hope i could help you :)
She might be uncomfortable, having a month off she would have lost muscle and your saddle may no longer fit correctly
You just have to let her know that it doesn’t matter if she bucks, and you will make her go anyways. Once you ask continue asking until she goes, even if it takes awhile. She willbuck/kick/stop but she will learn that it is harder to “misbehave” and easier to go after a few times. Once she starts to understand that she has to go forward, work on a lot of transitions from wal to trot. This will get her to respond better to your leg. Good luck and I hope this helped!