When a grown man has "feelings" for a woman he makes it known. If his friend is "wondering" about how he feels about her it's because he has not declared his feelings towards her.
Oftentimes people mistake attention for love or desire.
Some people really enjoy being around their platonic friends. Maybe they have a similar sense of humor or other things in common that they may not have with there spouse.
However it does not mean that he loves his friend more than his wife or would ever consider cheating on/leaving his wife.
This woman should simply enjoy their friendship and not allow her (mind) to speculate or wonder if there is something beyond the platonic. The reality is it is (her) that (wants) something more than a platonic friendship. Infidelity begins in the mind.
She has (feelings) for him! She is the one (comparing) his attention to her versus the attention she witnesses him giving to his wife. However she can never know how much attention he gives his wife in the privacy of their home and in their bed.
This may be an instance of her seeing what she (wants) to see. Some people appear nicer to friends and family members they don't see as often. Even parents have been known to appear nicer and more patient with other people's kids than they are with their own. Nevertheless it would be a mistake to believe they love those kids more than they love their own.