As someone who's no longer in contact with their own family, I'd say there's no easy way to leave, even if one comes from an extremely abusive family (which I did). I had nightmares about my parents almost every night for years, and I still get them sometimes. Even so, I still felt like leaving them left a huge hole in my life that nothing else could adequately fill. I'd been living with them my entire life, I'd been told over and over that I had to love them, that a good person would love their family, that I had an obligation to do as they asked and make them happy, and I felt guilty, hurt, alone, and depressed over leaving. It's not something I would recommend to most people.
The only time I would recommend cutting ties is when the consequences of staying would be worse for you than leaving. For me, I realized that every time I interacted with my parents, or with any other family members, I ended up getting feeling insulted, hurt, devalued, and more lonely than I'd been before I talked to them. My nightmares got worse every time I saw or spoke to them. After some time, I realized that staying with the family was wrecking me emotionally, and I stopped talking to them.
If you do need to leave, your mom would probably have one of three reactions to your decision, all of which could hurt you. She could act indifferent to your choice, which would make you feel unloved; she may beg for you to come back, which would make you feel guilty and break your heart; or she may grow openly hostile and attack you, verbally or physically (depending on her personality). You need to be prepared to deal with any of those three scenarios, and anything else that could happen.
Obviously, you also need to be in a place where you can support yourself financially and not have to run back to your mom when you need a place to stay. Having a supporting group of friends helps a lot. You can fall back on your friends when you need them, and they'll (hopefully) be there for you if you ever feel lonely or guilty over your decision.
One more important thing to remember: you shouldn't beat yourself up over your decision, whatever you choose to do. You'd be leaving because that's what you need to do, so you shouldn't blame yourself for that choice.