Moving out but guilty

I was wondering if anyone happens to stumble upon this, would you please help me out. I am 22 years old, and currently still living at home. I am going to be moving out soon, into a home of my own, and as exciting as that seems, it also makes me really sad. I am the child of a 56 year old woman, who is divorced, and currently is single. Over the years, it has always been just her and I, and she's grown from being my Mother, to my Best Friend. She won't have anyone else in the house when I leave, and I guess I feel sort of bad becuase I don't ever want her to feel lonely or left behind. I don't want her to feel like she has no one even though I will be about 20 minutes away. It just recently hit me that when I move out and start my own life, she will still be where she is today, and she will live this lifestyle of going to work, and coming home, and having no one to talk to and no one to laugh with. She will just sit there at home doing her own thing all alone, and I can't help but to feel the slightest bit guilty, but at the same time I don't even know what I am supposed to feel. I think about her all the time, and everything I do I try to make her feel included. My dad left 20 years ago, and she has been single since. I know in my heart, that I would not feel this way if things were a little different, like if I had a younger sibling that would still be there or if she had someone in her life that would still be there, to make her laugh, smile, and give her someone to talk to. I love her with all of my heart, and she means a great deal to me, and I am really close with her. Ugh, I just don't know what I am supposed to do in a situation like this. Also, with her being the age that she is, I know she needs my help doing laundry, and cutting the grass, and all the little things that I do to help her. Has anyone gone through this? Can anyone help me, please? Thanks- Britt