Bro, let me set things strait for you.

This isn't sexism. It's someone you're in a relationship politly asking you to do something for her. Something that she knows you are perfectly capable of doing. As you know she is capable of making you a sandwich. The difference is in the execution.

Let's say that we, you and me OP, are in a relationship.(For visualization purposes, please feel free to imagine me as your favorite porn star/supermodel/whatever the hell you want. I personally am imagining you as that one cute girl in my spanish class.) Let's say it's a decent one, we apparently live together, or at least live within walking distance of each other. So we've known each other for a while, and have this mutual respect thing going on, or at least I hope so. And we know what each of us bring to the relationship, in terms of practical shit, not just mindblowing sex or whatever. (It's probably not that mindblowing, but you know it's at least decent)

You know that I can do basic physical labor and heavy lifting because I am an ox. Dumb but fairly strong and hardworking. I let you tell me what to do because I am stupid and know that I would fuck things up if left to my own devices. And I know that you can fix the car and are sort of a jerk. But that's okay, because I luv you babe.

Now, because you can fix the car, I expect you to fix the car. Because refucsing would be a dick move. But that doesn't mean I'm gonna demand that you fix my car. Because that's also a dick move. I'll be all 'Bebes, my car's not working and I'm a dumb failure of a genderly ambiguous whatever OP wants me to be and don't know what the shit's going down. Could you take a look at it because I don't want to waste the money in our presumably shared account on a mechanic if I don't need to.'

And you can answer 'I would babe, but I;m all kinds of hungry. Why don't you go make yourself useful, and fix me a sammach.'

And I'd be all... 'Er, sure.' Because I am a pushover.