Agree, sounds legit based on the description. If the "other" half wants to negotiate with a contractor who already did the work, let her do so...while standing behind her signaling to the contractor that she is crazy.

Only question I would have is did they pull a permit? If not, that is on you as much as them, but might be a bargaining chip.

Supplies cost me about $2.5K to do my complete bathroom in 2009 that sounds like it was close to what yours is. Gutted and complete remodel, brother-in-law did the drywall. Took about 80 hours all in and I did not buy high end fixtures or tile.