Yeah, she needs to change her stick figures.
I have a friend in slightly similar circumstances - she runs a weekly club night in a function room above a pub. It attracts an 'alternative' crowd, including several trans regulars, but also for as long as anyone can remember, women have been using the Gents to avoid queueing, & men have been using the mirrors in the Ladies to check their make up. She doesn't want to change this, & nor would her clientele.
She & the pub landlord (who doesn't much care who wees where but wants to be legally compliant) have looked into it, taken advice, & she is now using temporary signage on the loos for her club night, which covers the stick figures & makes it clear both are unisex. The signs are temporary cover ups because other people also book the room, & so it defaults to male/female unless whoever books it wants unisex.
Your mate also needs to supply single sex facilities for her bar staff (can be an enclosed unisex staff toilet, so long as it's single occupancy). My friend is covered here as the staff can use the single sex toilets in the main bar, if they don't want to use the unisex facilities in the club room (as can any punters who want a single sex toilet - they just get their hand stamped to leave the club room & come back).
It's really not as simple as just 'yah boo sucks let's ignore the law'. Your friend could easily have her arrangements challenged by a disgruntled customer or member of staff.