It does sound strange doesn't it? The way she unveils herself to Celegorm... I mean, she could have known the effect she had on Celegorm. Wasn't she already in love with Beren? Why should she reveal herself this way and well, let Celegorm fall for her... she could have set him straight on that, telling him she already had a partner. And she rides with them to Nargothrond, voluntarely... Hmmm. All shall love me and despair is the first thing that comes to me.