What's my moms problem?

I'm a 17 year old girl about to go off to college. I'm the youngest of two. I have an older sister who is 21. We grew up in a single parent family so all my life it's been me my mom and my sister. When I go off to college I will be moving out into a student apartment literally no more than 20 mins away. My sister has been moved out for a couple years now and she has her own boyfriend and child. But something my sister and I have both noticed is how much my mom really tries to control our lives and have things her way. My mom literally wouldn't even let me get the comforter/curtains I wanted for my new bedroom because she didn't like it. But that's really on a smaller scale. It seems like she just wants to control everything and in a way it seems like she lives through us. My mom is single, isn't really into dating(due to a lot of insecurities) and also has friends but doesn't like hanging out with them. So basically when I move out it'll just be my mom and dog in the house and I know she will be lonely so I feel bad. On the other hand i feel I need to break away from her hovering and sheltering and live my own life and gain my own experiences but for some reason I feel guilty. I know my mom cares so I don't wanna just leave her hanging but I can't keep having her tell me what to do and how to live. She also tries to control my sister and she's a grown woman. She will try to enable a split between my sister and her boyfriend because she thinks he's a bum but in deeper context it seems like she just wants me sister and niece to move back home to be with her. I know I wrote a lot but I need some advice, some encouragement, anything! I'm just at a really tough position in life and as if I wasn't nervous enough about going to college now I'm extra stressed. Please help