He was very obvious about his feelings for Tim. Maaaaybe, Steph thinks, he could have been a little more obvious with her about his feelings towards her. More words, less ass palming.

"We're really doing this love confession, this-is-what-was-really-going-on thing right now in this creepy, abandoned castle... okay. Cool. I'm not one for romantic crap, anyway. It works."

Which doesn't really give Ezio much to go on.