Have you sat her down (without the girlfriend present) and had a real talk with her? As in "mom, I love you, but I can't be supporting you for the rest of your life. If you want to remain room mates, then I need you to start doing things around here like take out the trash, clean the bathroom, cook X number of meals per week and tidy up things at least once a week, and in the event that there are household expenses, like the washer and dryer we bought, then you have to chip in for your share. If you can't or won't do this, then I need you to move out, and I'll no longer be taking care of your rent or other incidentals. This is a standard thing for room mates - we all chip in and do chores around the house equally, or else we find new room mates."
And if she says she can't or won't get a full time job, then suggest a part time job. If she can't do that, then tell her that when the lease is up on the current place, she will be on her own, so she has until then to figure out what she's going to do. She's had 7 years to not work; it's time to get her shit together and get back out there and be an adult.
And you definitely need to do some research and reading on boundaries. I'd suggest reading a few books - Emotional Blackmail by Susan Forward, and maybe the book Toxic Parents (same auhor, might be more toxic than what you're dealing with, but there's some good insight stuff in there) because your mom sounds pretty messed up and that's bound to have screwed you up a little - I speak from experience on that one. ;)
Like if she comes over too often, tell her that she can visit on X day, but now is not a good time, and don't even let her in the door. Polite but firm - "So sorry mom, but now is not a good time. Should have called first and saved yourself the trip." and shut door. If she calls to say she is heading over and it's not a good time for you, same thing "Sorry mom, can't do it tonight. But what about Sunday?" and if she screams/cries then tell her sorry she's feeling that way, and you'll talk to her when she's calmer... and hang up.
And not sure how you interact with your girlfriend, but maybe make sure that she's not using you in the same way. You mention that she also lives with you, but you're footing most of the bills. She needs to be pulling her weight as well, an it seems a bit hypocritical of her to push you to get your mom to move out when she's not contributing her fair share and is also technically mooching off of you too.
Seems possible, but hard to tell from the info you provided. But if I was you, I'd move and just live alone for a little while to figure out who you are and what you want and build a strong backbone to keep people from using and manipulating you. (not judging you - just think you are someone that sounds like you are too nice for your own good, and some folks can sense this and will take advantage of you).