IMO, just because he says she is his favorita, it cannot automatically be assumed that she feels the same way.

I'm not saying she does not though.
My ex-favorita in TJ now looks like she would like to bite my head off, due to me going arriba with other ladies. I doubt she would have much good to say about me, although she still keeps an eye on me in the bar.
My favorita before her wrote me an e-mail about; "amor" when is your next trip? I IM'd a couple of days later, without my name. Her response was, "Who are you"? I still get a great laugh about that. Today I got another IM from her.
While they both treated me great in sessions, which is how they became favoritas, I doubt seriously if they considered me their favorito (is that a word?).

Just another Gringo who fortunately got them off in bed, and even better, they got paid for it.
IMHO, if there is any doubt, make a low ball offer. It will be a good test about how much she feels about you.
Health & happiness....