If you found her "lost in the city" she may have gone astray. Or got dumped.
Because a homeless semi-ferale wouldnt look lost in streets. It would live there.
If dumped, hopefully you will want to be the new owner.
But if she got astray, perhaps sneaked out because she rode loose in a car and somebody opened the door... Please do seek after the owner.
Please set up messages: "White cat found". Dont describe too exactly how she is looking. Let the owner identyfy her. Let him give accurate description. Use a prepayed mobil phone card if possible.
If you get her a check up with a veterinarian (recommend!), the vet can see if she has a identyfying micro-chip. IF she is purebred, she probably will have a microchip.
Does she seems to have parasites? Fleas, worms? If not, she was astray/dumped very recently.
If yes - be careful with what medicines you use. Use only such recommended by a vet or buyed in a pharmacia/apothece. Dewormers /anti fleas buyed in pet shops are often dangerous.
OK. What breed look alike your beauty is? Dont know.
Turkish angora perhaps?
I suppose there are such as white longhaired oriental? It has surely some fancy name - another than
longhaired foreign white? ah, Javanese is longhaired oriental, thus
perhaps a look alike of a white javanese??
Two guesses on this beuty.
Good luck!