Consider yourself lucky. She’s a friend. if things get worse and you have no other option but to cut her out of your life, then you can do so. Unfortunately for me, I have people like that in my FAMILY! I cannot escape them even if I want to.
Seriously though, even if it is a joke, if you don’t like it, say something. You don’t have to get worked up. just calmly take her aside and tell her that you don’t find her comments amusing and that you’d rather she didn’t say stuff like that.
It could be that she doesn’t realise how offensive she’s being. You get people who open their mouths without engaging their brains, but once you point it out to them (tactfully) they usually learn from it.
There’s a good chance she could just try to brush it off by saying that it was just a joke or that you’re being oversensitive, but then she’s just showing her immaturity when what she should be doing is apologising for making you feel bad. It’s your right to say something if someone upsets you with insensitive comments, so don’t let her turn the tables on you.
if all else fails, give her a taste of her own medicine – publicly! That might seem pretty low, but there are some people who only learn the hard way!