First things first: my kid sleeps in my/my spouse's bed when one of us is out of town, or as an occasional "treat" (to her). SHE'S NINE, and more importantly, it's because she wants it. Much as I love being able to reach over and just put my hand on her shoulder for a second when I wake up, I won't mourn all that much when she grows out of it - she still has that kid habit of sleeping in weird positions, and thus taking up a lot of the bed. The day that I even suspect that she's doing this for me (or her father) is the day I put a stop to it.

But that's really just the icing on the "OMG, bad bad bad!" cake in LW's situation. You feel guilty going out to study? What's going to happen when you get a job and want to move out?

Sadly, I'm not sure there IS a middle ground in this. This is just a guess, but I have the feeling that mom is going to wear down any partial boundaries the LW puts up. If she can afford it at all, LW needs to move out. If she can't afford that, she needs to find a way to block the guilt and just stop enabling mom's behavior. Go out when you want to, refuse to sleep in her bed, etc. This is all easier said than done, which is why a therapist, especially a CBT, would be good for you.