John. Seems you have tried a number of times to get your girlfriend to move out and each time has failed as you caved in.  At this point, she’s never going to believe you mean that she needs to go as history and experience now tells her that so long as plays on your soft spot, you will cave again and she will not need to change anything.  So the time will never be ‘right’, she may get a fantastic job, earn enough to support herself and so on but whilst she still hangs on to a relationship with you, she will still stay.

The thing with soft spots is, sometimes it’s also a way of trying to hide from being the ‘bad guy’. Whereas there is no ‘nice’ way out of this one. Even if you get her mother to agree she can come back – she is still going to think you are a bad guy for a while, after all, you are rejecting her, finishing the relationship.  So you need to work on accepting there is no ‘nice’ way for you to do this, you can absolutely be as respectful as needed, especially with the kids but you are going to have to set clear boundaries that this relationship is over.

Have you actually finished the relationship with her or are you still together as a couple?  As in, at least as a first step, be clear that the relationship is over regardless of everything else. You can still be living in the house together but not being together in a relationship. You can start dating others if you want, then being a single guy, though do tend to agree some time by yourself is not a bad thing, so just going out with friends, doing things by yourself, spending less time with the kids and no time alone with her. If no spare room, put up with sleeping on the sofa for a bit. You need to bring it home that the relationship is over, that things will be changing regardless if she moves out or not.

Being clear and setting boundaries is not the same as being heartless. You know by being nice you are actually being cruel in the long run by dragging this out for both of you.

Hope helps.