I don't believe it's possible to stop yourself from thinking or feeling a certain way. People can repress or suppress their thoughts and feelings for some time but they can't make them go away. Thoughts and feelings are energies and when they are suppressed they get stored in the body and become so toxic overtime that they eventually turn into diseases or they find unhealthy, destructive ways to express themselves. One example of this would be a passive-aggressive behavior when the person doesn't allow themselves to feel their anger or even to be aware of the anger but instead lets the anger to come out in destructive ways.

Whatever you are feeling, the best thing to do is to accept the feeling without a judgment and allow it to be. Then, it needs to be processed meaning completely understood if you want it not to cause you problems. Find time for yourself to be alone and to reflect on your jealousy. Ask yourself what it means for you that your T has a bf and what it would mean if she didn't. If you would like to have a partner like your T, ask yourself why and what would that kind of partnership give you that is important to you. You may want to write down your reflections in a journal.

Use your jealousy as an opportunity to learn more about yourself, because, after all, I believe that everything that happens to us is an opportunity to learn more about ourselves and our true needs.

Ideally, this kind of work is to be done with your therapist, but I am skeptical of how effective it could be if you do it with the same person who is the object of your attraction despite what traditional therapy suggests. This type of analysis requires the impartiality from the practitioner and if they are on the receiving end of the strong feelings from the client, they are in no position to be impartial no matter what the profession claims. That's just my opinion.