Warning this is a long read

I've never met anyone in my entire life who gets angry as easily as my girlfriend does. I have a relative who suffers from brain damage from a car wreck that causes him to have a short fuse and he doesn't get angry as easily as she does, and he has FREAKING BRAIN DAMAGE.

I feel like I can't talk. It doesn't matter what I do she gets angry, an example is this. Earlier this week I took her to dinner and after I got back from the restroom I asked her, ''why do you think they bother marking the restrooms, male or female since the restrooms here are single stall and only one person can use them at a time?'' She said because women's bathrooms are required to have baby changing tables, I said,'' really? they had one in the men's room to, It's a good idea, but I don't like that the businesses are forced to install them.'' (Yah I'm one of those people who doesn't like government regulations.) Now at this point her expression immediately turned sour, and she got very upset. She then began arguing with me and steadily getting angrier, until the subject was changed to anime, one of the only things I can talk to her about with her getting angry.

I'm not upset that she disagreed with me, I have disagreements with my friends all the time, its that she got almost violently angry over something so stupid. This isn't a one time problem, that's just the most recent example, I can't talk to her about anything without pissing her off. I talk about politics, she doesn't like politics so she gets pissed, I talk about big dreams, and if it doesn't suit her, she gets pissed, I'm talking to SOMEONE ELSE about something she doesn't like, she gets pissed, I laugh at a joke on tv that she doesn't like, she gets pissed, I talk about anything that doesn't interest her(ie things that aren't anime, cartoons, or video games), she gets pissed.

It's not just me either she gets pissed at my friends at the cafeteria every time they say something she doesn't like, and she tries to make them stop talking.

I used to try and ignore it because I haven't always been the best boyfriend, I've never cheated on her or anything that severe but I still had plenty of issue. She asked me to work on those issue and I did, I fixed them but she's still the same and its annoying me to death. I love her, I do but this isn't right.
I've asked her time and time again about the way she get's angry all the time, she says she's sorry but she can't help it.

is it normal for my girlfriend to get angry at everything all the time?