My girlfriend is sometimes racist to me

So like when we started going out I knew her family was against it but she was cool, smart, and interesting so I never associated her with any of that. And I don't know if in the beginning she was trying to be nicer or whatever but it's clear to me as we became more comfortable around each other that she started to say and act the the way she wanted without even thinking about how I might feel. What I mean is that she got into a habit of throwing around some racist remarks whenever we're alone in a sort of casual or joking kind of mood, like I can tell she isn't being serious at least, but as she started doing it more and more it made me get slightly more uncomfortable with time. I'm not the type to get easily offended but this has been bothering me like I feel I'm being taken for granted maybe. I also don't even know how to approach her about this because it will be awkward and I don't want her think I'm weak like her words are hurting me, which they are not, because they're more like just getting under my skin a little.