What’s the right choice?

My dad passed away about a year ago in December. Him and my mom were together for 37 years. I’m about to be 21. I live with my older brother her & my sister. They’re both in their 30’s and never moved out and don’t even work. I have a boyfriend and we want to move out together but I feel bad. I feel bad leaving my mom and growing up because she always tell me I can’t leave until something happens to her. I don’t want to be like my siblings. Me and my boyfriend keep talking of moving out to this place together and only thing stopping me is guilt. I dont know the right choice to make because my mom will be devastated because she never had a child leave before because my brother and sister didn’t do nothing with their life. I feel like because of that, I’m going to suffer. I even mentioned my boyfriend moving in there and my mom said no she wants it to be only the family. My boyfriend and I been together for a few years but I feel guilty to leave and I know this isn’t healthy so what would you do? I don’t want to hurt her but I also want to go live my life.....