The solution used for children in an adult sleeping bag is to tie a string around the bottom to reduce the dead air space. If you don't mind the extra weight and bulk, this is a possibility.

This is undoubtedly a well-used bag, so you need to find out the condition before buying! A careful laundering (follow the directions on the Western Mountaineering site) will often restore the loft, but not if the shell has gotten holes and therefore lost a lot of down.

As for warmth, check the EN13537 ratings, which you should find online on the Montbell site, if not for this model bag at least for comparable models. As a woman/cold sleeper, you need to know the comfort rating, which will be a lot different than the advertised rating, perhaps as much as 10 degrees different (25*F instead of 15).