I'd bet more related to not having the toilet for a couple of days
She sounds like she's talked herself into not going so she didn't have to use the bucket and now she's having a bit of trouble since the loo is up and running again.
Funny things go on in their little heads at this age about toileting LOL.
She'll probably go by tomorrow. FWIW my two year old sometimes goes two days without a poo - then she'll do a total doozy to make up for it!