Do some girls go into boys’ toilets or locker room?
 

I have many experiences, one to start with.

Yes, I got conned into helping a friend out on a summer holiday club thing she did for local children who's families couldn't afford to go on days out or holidays.
She some how always seemed to decide to come into the Male shower to talk to me about the days debrief and the next days plans while I was showering,
She wasn't the only one, sometimes other helpers would join her or decide they need to help with something in the locker room.
Funny I was the only man who was asked to help apparently as they was only ten boys at the camp they only needed me to help with the boys :)

Used a Stall
 

On occasions I have used the men's room when there has been a long line outside the women's room. At least twice a woman has walked into the men's room and utilized a stall.

It's fairly common in NYC theaters where there are long lines for the ladies. No one bats an eye.

DR

Agreed, it happens a lot in the UK, in many different reasons and situations.
It really isn't a big deal, no one cares or takes any notice

Ibiza
 

I used to go on lads holidays alot in my younger days. Everytime I needed the toilet is wasn't uncommon for a group of 3-4, women in there. It also uncommon for then to poke there head round to watch you unzip etc. It was always busy in there.