The tactile surface would indicate a crossing; it’s there so that blind people can differentiate between pavement and road in the absence of a difference in surface height.
Ergo, she parked on a crossing, which is illegal (THC rule 191).
However, the ticket is for a different offence, parking next to a dropped kerb (THC rule 243). Therefore, whilst she has committed an offence, the ticket is unenforceable.
If it’s issued by the council / police / TfL, challenge it. If it’s issued by anyone else, throw it in the bin.