https://en.wiktionary.org/wiki/UMA
Apparently, "Unidentified Mysterious Animal" is the correct translation. You got it right!
It also just means "cryptid" but since they had a big "U M A" sign in the back, it makes sense to keep the acronym.
She really should have joined ultimate Frisbee. I also feel kinda bad for the sports teams that she didn't join. Like they said she could have taken them to nationals.