It sounds like your jealousy is indicating that you are feeling insecure on some level. The way to get around that is to try to enforce your feelings of security. How you do that is very individualistic.
If you are the logical type, you could think abut the good times you have together and realize that there is no reason for her to give that up.
You could talk to her and talk about what each of you likes in the other. You could tell her you are feeling a little insecure and would like to know she wants to be with you.
Some of your jealousy could be envious over her other partner. Dealing with that takes other approaches. You could try to feel compersion by being happy that she is happy. Or you could realize that what you two have together is unique and that is something that is not between them. Or you could try to focus on the idea that since you are apart more often, your time together will be that much more special.