It's quite challenging for Ukrainians to be issued US visas, but not impossible.
You'll need to prepare the paperwork/application along the same lines as what you did for her TRV: Strong finances, including funds to afford the visit + her strong ties to Ukraine + well-defined purpose of visit, etc.
They'll run checks on you + her before she gets to the interview. Questions could be more inclined towards you (and not her strong ties, etc) + her Canada visit at the interview. Documents may not get asked/checked at the interview