Should I be offended by the way my gf acts?

Okay so my girlfriend and I have been together for about 2 years now, and everything is good,usually. Like I still love her, I still even say love u at least once a day, and she does the same, BUT I can't help but feel like I'm not as important to her as she is to me. Here is an example: We were arguing one time and she was like "you can easily be replaced" now I don't know if she was trying to cut deep or if she really meant it, but I didnt like it at all so I didn't let it go unnoticed so I asked her what she meant by that, and I told her if she didn't want to be with me anymore, I would prefer her to just let me know, I was on the verge of ending things when she said that. And thats not the only thing, recently we were joking around, at least I thought, and she was talking about putting me out her life, even though I think we were still joking, I don't really joke around like that, I have never said some bs like that to her, but then it turned kind of serious and she said it again so I told her to do it, she tried to take it back, and then I told her no, she keeps saying it so much I want you to show me, like that. So am I wrong for getting a little mad when she says **** like that or am I overreacting?? Because I feel like when seriously arguing, if the person keeps bringing up the same thing, they want to do it, but then again she is known for saying things just to piss me off, especially since she knows I HATE that kind of stuff. So should I be offended, take that as a warning sign, or should I just blow it off? because we still aren't talking and I wanna know if I'm wrong I will make it right but if not, I won't feel as bad. thanks for any help.