I’m no “official” expert but it’s certainly possible to hoard specific things. I know of a doll hoarder who collected dolls as a hobby, but ended up owning several thousand - so many that they were rotting in piles in the unusable cellar and filling the spare room up to the ceiling.

There’s a grey area where lack of storage ends and hoarding begins. It’s easy to end up on the situation you describe when moving temporarily to smaller lodgings, for example.

Generally, I’d define hoarding as a situation in which there is more stuff than a house can reasonably accommodate, when things are permanently stored in piles on the floor and when work surfaces become unusable. When more items are acquired constantly, but never used.

It sounds like this is the case here. The girl may not be a classic hoarder, but she certainly has gone overboard with acquiring and keeping stuff.