Is it normal that i can't stand being around my mom when she is crying?

Well I rarely see my dad cry, so this post is almost entirely about my mom... My mom is that type of woman that likes to cry about anything. It's not depression, or anything.. She just cries for several things. Honestly, call me sick, a sociopath, or whatever, but when she cries I just want to walk out of the room. I'm not much of a crier myself because I don't like having people feel sorry for me or try to console me. It is a very uncomfortable feeling for me. Anyway, back to the point. She cries for everything!! I get that people need to cry and hey that is fine with me.. but I am the oldest of my siblings, so when she cries, guess who's shoulder she has to go to. It's been this way since I was a kid!! She has--and I am not kidding-- 2 sisters and 11 brothers!! That's a big ass family she can go to about her feelings. Especially since lately her crying has been more about the loss of thier mother. I'm sorry, but since I was a kid I was the one who has had the burden of listening to her cry, complain, and vent about EVERYTHING, so yes even her mourning the death of my grandmother has become a bit overwhelming.. I have been there for every complaint, cry, or moment of just venting since I was young. Examples: when my sisters did something wrong, she had a fight with my dad, when she had a fight with a family member, when she remembers someone she lost (even from several years ago), when she suddenly realizes all the mistakes her parents made on her, or when she even thinks about the mistakes she made on us... the list goes on!! I'm sorry, but as a kid, that was a lot to take!! I am 22 now and it has all become too overwhelming. I have my own problems to deal with and I am still expected to be the rock/emotional support for my own mother., And please don't give me that crap about how I am a sociopath or my mother deserves my attention after all the emotional support she's given me. A- I do have empathy, sympathy, and just feelings for others. I am not a total monster. B- I was never able to count on my mom for emotional support. There were few times when I tried, but she didn't have anything helpful to say and would even turn it back to her.. I can't even tell her how I feel about her constantly going to me when she is crying or upset about something. I have tried. Believe me I've tried, but then guess what she started to do.. Please.. just take one goddamn guess..
It's finally gotten to the point where when she wants to vent or cry, I tell her to call my aunt-- who by the way is her fucking twin sister!! Yea a twin. They have been close their entire lives and are still really close and yet I'm the one she goes to when she wants to cry. When I tell her to call one of my aunts or to go visit another family member, she tells me I am mean and tries to make me feel guilty. I'm sorry but I can't even feel guilty anymore. I just don't want to be around her when she cries anymore. I can't even be around other when they cry, now. Just a few years ago, I was really good at being there for people when they were upset, but now, I try to put some distance between us. I don't even like getting close to too many new people because I don't want to have too much on my plate when it comes to supporting others..
I guess I am trying to figure out if this is normal or at least common. I highly doubt I am a sociopath because I do sincerely feel empathy and sympathy for others.. I just can't be around them, especially my mother, when they cry. I've had enough.