Is she fully supporting you or are you and your bf working? If she's fully supporting you I'd get a job first and show some independence before I tell her. Try to establish some rapport by showing her initiative and responsibility. If you're already doing all that you can then tell her now and make a plan to get your own place with your bf if you're living with her and can financially afford to be on your own. Have some sort of plan going forward that you can discuss with her, it might reassure her doubts about you. I agree with pp that people say mean things when they're stressed or angry, ignore that she said that to you, what's done is done and you can't reverse time. She can, however start treating you more respectfully if you're doing all you can to show you're doing everything in your power to be successful and carve a path.
It'd be shameful for her to not support you if that's what you're trying to do and please be aware that even in the most positive circumstances people will be cruel. My own mother has said nasty things about how she's going to refuse to babysit on occasion, refuse to buy my kids toys, clothing etc, do this that and the next thing for our children even now that I'm 41, fully established, have 2 degrees, gainfully employed (17 years with the same company), happily with my partner for 19 years (married for 10), and own 2 properties. I usually give it 24 hours before I confront her every time she's nasty and tell her how she's hurt my feelings although I'd prefer to use some choice four letter words with her. But being confrontational is not the way to get her to show compassion and get her to support me when clearly she seems to have a problem with that from the get-go! Do what you can to win her over, but realize that it'll be much easier once she sees your beautiful baby in her arms and you might have to put up with some crappy tone until then (I certainly did)!
