Oyster toilet discrimination?

That's a bit more than the usual "spend a penny"!

No station staff to let her out and back in?

Been caught out the same way when caught short at Harrow.

At least at Baker Street there is the option of an OSI to Marylebone

It depends on when you got your Olympic and Paralympic tickets. If print-at-home then no.

I think there is also an OSI between the gatelines at Baker Street. So you could have touched in on the bakerloo line gateline.

Although surely much simpler just to ask the staff to let you out to spend a penny?

That was my first thought but it is not shown on the OSI list linked elsewhere in this forum.

Perhaps the main doors to toilets could be fitted with an oyster reader/lock? That way if someone has to exit a station a timed OSI could be setup to loos outside the gateline. Also it would provide some kind of record of who used a toilet if there was vandalism. Not perfect, but would avoid charges like that above. Avoid the awkward process of fishing around in ones pocket for the correct silver to pay a 'toilet warden' who doesnt speak english to let you in...

It's discrimination because one gender had to pay when the other didn't, regardless of which way round it is.
My guess is that they were changing at Baker Street because they knew there were loos there. Although the toilet facilities map shows male and female toilets inside the gateline at Finchley Road they may not have known that and/or been able to wait that long. The map also doesn't note that not all toilets are open 24h, as I found at Canning Town last night - I had walk to the McDonalds as the toilets in the bus station close at about 7pm iirc. certainly well before 11pm when I got there.

And she would have slipped into the Gents if we'd realised/thought about the cost of touching out and in again for a two minute period.

And yes, took first train out of Liverpool St in order to use the facilities at Baker St.

Anyway, TFL have kindly agreed to a peefund of the £2.60, so that's, er, a relief then.

BTW, when I paid homage to the A-stock at the end of July by doing train 442 (I think) Aldgate-Chesham after seeing it on it's way to Uxbridge earlier I resisted the temptation to take it to Aldgate initially and even though I starved myself of liquids after seeing it earlier I went to Liverpool Street on the S-stock first to "clear the path" and make sure I was not caught short.

That said, one thing I sometimes do at mainline stations to avoid absurd toilet charges is to nip onto a train to use the toilet..... but check that it isn't due to leave when you do that!