Actually, up is a perfectly good word.
Without up, we could look at a dictionary, but we’d never look up anything.
Without up, we could step but never step up to a task, and who knows where we’d end up.
We couldn’t speak up or roll up or move up; nothing would ever turn up. We could shut but never shut up, get fed but never fed up. The sun would never come up.
Our existence would be all too flat if up were put down.
For all its usefulness, though, up makes a ghastly verb when used to mean increase or improve.
As if transformed, that cute, handy little word suddenly communicates with all the eloquence of a suppository.
Actually, substituting suppository might be a good way to check yourself if you consider writing upped the budget or upped her salary or, as in this case, upped her repertoire. Writing suppositoried her repertoire should give even the most uppity writer pause.
Go ahead and up the ante if you feel like it. Poker would have disappeared long ago if that idiom weren’t an option.
Otherwise, though, stick up the verb in a dark drawer somewhere and forget about it. Your audience will thank you.