Actually, seperating them would be one of the first things I'd do (force feeding being the absolute last). Maybe she's a shy feeder and doesn't like to feed around other geckos (every gecko has his/her own personality right?). Heck my gecko knows when I go to have dinner and has his dinner while I'm away. Did you try wax worms? Addictive yes, but you can use them to see if she'll eat atleast something.
Also, it's normal for new geckos to not eat for a while (up to a week for adults) when they move in to a new home.
BTW, where'd you get them? Last time I heard you turned down those off looking geckos from someone after you did some website work for them. I hope the geckos you have now are alot better looking that those did.
-Lemur 6