These are exactly my thoughts. People can move on from romantic/sexual relationships to platonic friendships and not every future partner will be threatened by that. I could understand severing the relationships with Jake and Lena if Sabrina was still in the picture, but don’t preemptively cut them off because you think a future hypothetical partner would have a problem with them. As long as you’re open from the start, you’ll learn who’d have an issue with it and who wouldn’t and you can decide then which relationships are more important to you if it comes to it. For now, your friends will be the ones most understanding of your current situation and able to help you heal. And for the future, be honest with your partner about your situation.