Some background info:
So, I'm working on this novel, where the main characters have been through a lot together. And when I say a lot, I mean, traumatic things they'll never be able to quite get over. They both have have symptoms of ptsd but they can't get medical help because of their circumstances (for example: one of them is wanted by the police. Things of that nature.) Where the novel is going, I don't see them being able to continue having a healthy relationship (which is heartbreaking for me because they are my babies and out of all the couples in all my stories they are my favorite, but I have to acknowledge it just wouldn't be realistic to have them have a happy ending). Party A has realized this, but recognizes that if they just leave party B, party B isn't going to quite be able to handle that since Party B is convinced Party A is all Party B has. So to end to story, I want to somehow have Party B forget about Party A. I've considered having an outside force I've hinted at throughout the story strike Party B, and have them barely survive but with selective amnesia. In this scenario they would forget everything beyond the point in which they initially met and started liking Party A. Before their feelings became obsessive and dangerous and everything happened. Then Party A would leave and the story would end. Party A would still miss Party B but figure it's for the better and Party B would get over Party A since their feelings for Party A would still be at an initial stage.
However, I'm concerned that it might be unrealistic to have Party B never regain their memories. And if Party B were to regain their memories and realize Party A left them it would just cause a whole new arc because there is no way Party B would react positively to that.
Furthermore, amnesia is such a big cliche in writing, and while I don't think cliches are a bad thing, usually if I'm implementing one in my writing it's purposely, and it's done in a comedic effect where the characters themselves realize it's the most typical thing that could have happened. This story, however, is meant to be more serious and I'm scared some readers may be disgruntled if I have a character get amnesia right towards the end, especially when things seem to be looking up.
So, therefore, that's why I have to ask. Does anyone know of any alternatives to the amnesia cliche? Other ways of having a character suddenly lose strong feelings for another?