Good guess, but a trifle is sponge-based, rather than shortcake, and it isn't frozen nor does it contain ice cream in the usual American sense of parfait nor is it layered with cream. It's quite diferent from a sundae. The cream, if used, is simply a top-layer. If you take a look at the other comment (link above), there's a more detailed description.
Parfait in the UK-sense is traditionally a meat paté, although use in the US sense is increasing as it often appears as a dessert occurs if American restaurant chains.
Parfait, simply means perfect in French. Unusually, Anericans have gone with the French meaning with one, whereas we've chosen to apply it in an earlier sense. Trifle is very much older than the French dessert.
Yes it is sponge cake based sometimes added fruit and cream. It is British but we also have it in Australia and New Zealand. Maybe in Canada too with its part British background but I dont know.
Why does this sentence have to have some in it? I agree it is a possible answer but couldn't you just say she wants trifle. I have asked for it to be accepted but lets see.
That is already one of the accepted variations. You may have made a mistake in the sentence, or Duo may have had a glitch in recognising an accepted alternative. If you use the app, check that you have the latest version - there are frequent updates and bug fixes.