I would just think of the fact that she is doing it in front of you. Why would she be openly affectionate to a male who wants her or someone she wants in front of you? This fact should make you realize that its not meant in that way at all.

Have you talked to her about it? My guy friends and I tell each other we love each other and my boyfriend does that with girl friends of his. I just know that if there was something going on he wouldn't be that open about it with me.