Mom issue

So I’m 17 and 18 in July. I graduate next year and I was thinking about moving out a few months later. ( graduate in May move out in like January of 2020) well when I kinda bring it up she’s really mean about it and starts telling me how I’ll never be able to do it and it’s so expensive and she don’t know where I’ll be getting magic money from. I don’t know if it’s a mom thing or she’s just being extra