How to tell my mom?! 😳

So I had my first child when I was 18 got a lot of help from my parents. I am now 25 and live with my boyfriend. We have been together over a year. This is something that we planned and I have kind of mentioned in passing that we wanted kids but my BF didn't think it was possible. Her face every time I have mentioned it just seemed like horrified. I don't need her help anymore and I am an adult but I just want her to be excited for me and not freak out lol. Any suggestions as to how I can break it to her would be appreciated. She's not a mean woman I just don't think she will be grateful at first 😕