The reason she might have told you she likes this boy may be a) because of the rumours or b) because she likes you too and hopes that by telling you she likes that boy she'll get you to tell her you like her.
But if you truly only want to hold her and be with her all the time, well, the only way you can make that happen is by actually telling her and take your chances. Whether that's smart? It's hard to say.
Frankly, the best advice I feel I can give you is to talk all of this over with a RL objective third party who knows the situation and so on. If there's such a person whose advice you'd value and whom you can trust not to tell private details to other people, talk to him or her and explain the situation.
Those are my two cents.
PS. I deliberately avoided the two letter 's' word that seems to have occupied most of the discussion in this thread.