YTA.

Look, the reality is that as a human, compared to an Orc, you ARE small and weak. Obviously SHE doesn't have a problem with this and sees other qualities in you. If your family is going to hold that against you, then that is THEIR problem and not yours. Or, if as I suspect, you only THINK it makes you "look weak," but the rest of your family just thinks it's a neat thing that happens, then you're very much being an insecure asshole here. I mean I get it, but c'mon; you knew what you were getting into when you started dating her. Maybe not the deadlifting tradition in particular, which btw dates back thousands of years, but the idea that as an orc, she is physically much stronger and more enduring than you, and people would see that, including your family.

The fact that she didn't break up with you over this means that she still has hope that you'll get over yourself. All she did instead was essentially say "Oh, well since I have to abide by all your cultural norms when I'm with your family and suppress my own rather than share them, it's only fair you be held to the same standard." Which is actually a really great opportunity to make amends. So I'd recommend you really throw yourself into her traditions for a little while. Run those laps! Go for the biggest hog! Drink the yellow drink, not just the red (tar'jahgg and kae-oor, respectively)! After a while, you should talk with her and tell her your sorry and that you'd love it if she continued to share her traditions with your family. And honestly, I bet any little kids get an enormous kick out of the deadlifting.