I can understand why you'd see that stuff as a sign of intent and I hope you don't think I'm trying to be offensive but
ye u messed up
It's not really your fault that you messed up, given the circumstances - I mean, 90% of this **** is guesswork and the heart thing in particular does seem a really weird thing to say
But just, don't.
Ever.
It saves you the hassle of guessing peoples intentions in the long-run and forces people to either be straight up with you or risk the possibility of alienating you which in some cases actually serves to make you more appealing because of the perceived challen- blah blah blah red pill bs, you get the picture.
it's possible that at the time she totally meant it that way, then had a change of heart - but the issue is that without being specific, you can't really fire it back at her w/ the merit of proof, so as far as a truly objective viewer is concerned she's not technically* at fault, if a little unhelpful for reading your intentions either.
Say, out of interest, do you reckon she could've possibly been open to FWB but -not- a relationship, then when you asked her out she changed her mind about it? Although it's pretty lame, I know a lot of people who keep "potentials" on imaginary cloths-lines whilst they decide sort of thing.