i know a few people that get loads of money for doing well but my parents don't really do that. for my results last year, instead of just giving me a present they kind of just treated me to things e.g. lunch/clothes/money to go out.
and i remember when my brother did his they agreed to pay for his reading ticket if he did well (im hoping this will apply to me for this year lol)
so i think it is a bit nicer to be treated rather than get say, £200 pounds in bulk, im not sure why though because it's basically the same thing.
if you wanted to get her something physical, maybe a nice card? just because although they are simple they are really lovely to receive. or maybe bake her something?