It might be time to talk to a vet experienced with Yorkies for a good general checkup to make sure that there are no health issues.
You don't want Ruthie to become too dependent on Nutrical..... try giving her just a tad less ans see if hunger will kick in. You might also get several types of good quality dry pupy kibbles -- samples maybe -- and try to find one one that Ruthie is interested in.
Good luck and please please keep us posted on Ruthie's progress.
