I have a jelous girlfriend, who doesn't let me talk to others, in fear of me cheating on her. What should I do?

Tell her that you don't like her jealousy, and that you can't accept it.

Talk to her. If you want your relationship to last, communication is key.

Break up with her, if her jealousy is so bad that you're having to ask people what you should do about it, than it probably won't get better. People don't change, they can mature but she seems really insecure and you don't want to be reassuring her all of the time.

Man up - she doesn't own you. Reassure her to the best of your ability and then decide what you can or cannot live with. Maybe you can't live with this level of jealousy.

The absolutely only way for her to get over it, is a lot of reasurrance, and taking baby steps about doing somehting she is uncomfortable with. Not only for your sake, also for hers because while you may be annoyed with it, she is suffering, so it's something that really needs to be dealt with, it WILL ruin your relationship.