bed bugs are taking over

Tbh no way to tell, re bite patterns and reaction, bar seeing the bugger that bit you - this comes from watching a lot of people being bitten in a lab setting. Your reaction varies depending on species of insect, how long they feed and how much you scratch (knowingly or inadvertently). Hope she feels better soon though, blistery bites are no fun.

Is this in the UK?

Steam cleaning very effective with fleas. We had them in the bedroom at one point and they seemed to be in the carpet on my wife's side of the bed, and tended to bother her and not me (often the case that bloodsuckers go for women more). I got a cheap steam cleaner and was able to completely eradicate them with a couple of passes over the carpet and bed.

Yes though she did get bitten in Greece by mozzies and had several large bites but not blisters.
We put a bowl of soapy water down on the floor below a lamp but nothing visible and neither of us have actually seen any insects.

Everything is bagged now so, no, I did not see any signs of the buggers in my hotel, on the metro, or in a cab. 🤞 No one I met with mentioned the issue either.