Seing that I am a girl I know how women work lol. Personaly , I think in her mind you are not being affectionate enough to her. Do you tell her shes beautiful! And u love her and no one else sweet stuff like that? (by no way am I saying this is the case becuase I dont know). Even if you do a girl still wants more!! Its hard making a woman happy!
Its usually a girls way of saying that other guys find her attractive . She wants you to think the same way! This other guy may not even exist or if he does she has no feelings for him or else she would leave you for him.
She might just have alot on her mind. It all depends on the situation. But, me myself I dont think she likes this other guy. First off if she did she wouldnt tell you. Shes just mentioning him to make you know that she can find someone else to meet her needs. But , really she doesnt want no one else she just wants u to try harder.
Yeah, you should really try to talk to her! Let her know you care!