Lady Sif
In a nutshell, Sif is "An Asgardian warrior, Thor's childhood friend and Jane Foster's romantic rival, based on the deity of the same name". Sif is very much in love with Thor, and in the movie as well as in the comics, will do anything to help him, including help Jane Foster. In the movies, Sif is portrayed by the talented and beautiful Jaimie Alexander.
More soon!