"Anna works from home, that's why she gets up when she wants to."
Translation:Анна работает из дома, поэтому встаёт когда хочет.
It's really optional here (not sure Duo agrees). Cleaner without it, in my opinion, but I'd probably include it in speech without noticing.
You could correctly say, "Anna gets up when she wants to get up." But we already know "get up" is the thing we're talking about, so we drop it. We can also drop the "to" in this case without changing the meaning. It just might thud on some ears, just as including it will thud on others.
Consider, "You can leave if you have to [leave]." Getting rid of the trailing "to" there requires that we say, "... if you must."