I'm quite well versed in both dialects, I've been to British and American Schools.
I haven't heard of 'cookie' as prostitute but I do know that 'tarte' or 'tart' means prostitute. Also, as clarified in other posts, biscuits are sweet and are totally different to the American biscuits. Jelly is never used to refer to Jam in the UK, jelly is the American Jello-o.