I had the same exact experience, and I made myself miserable before going away because I felt so guilty. But, it worked out...we both got used to it and when I came home we just picked right up where we left off. Plus it'll encourage your mom to develop her own life a little bit more, to figure out what makes her happy and feel fulfilled aside from the basics like work and family. When it comes down to it, you just have to suck it up and do what you know is right for you, and what your mom would want for you, and I promise you, it will be ok!!! I understand how tough it is and I can't say that it will be an easy thing to leave home, but if it helps, think of it simply as going to school, not moving out, or leaving, or anything like that. Home is always home, after all!
Good luck, and hang in there!