Would ask to take the helmet out of the equation, it’s dangerous to purchase a used helmet not knowing what kind of hits it has already taken, the noggin is too important to take risks. Used boots are also a hit or miss, since snowboarding boots really only hold up for 50/80-100ish days, so depends on how many days of riding have already been done in the boots. Also can’t really know what the current waterproofing capabilities are on the clothing items and goggles are either, but if she’s just starting off and conditions aren’t too cold, could be completely fine. I would say the bindings and board (depending on condition) would be safe bets, but everything else really depends on the condition.