There is a fixed point for most characters where after breaking up doesn't come up anymore. Mostly, if you have already had sex with Raene it probably won't be possible to break up with her, unless in very specific scenarios. If you don't want to load up an older save you could probably set the variable via the developer console (press Shift + O to bring it up) by typing: raene_romance = False. The relationships status should be set to "No" in the relationships screen that case.