Just another idea...is she teething?
My DS1 did this leading up to 2yrs (he's 27mths now). Went off most foods he has always loved....then suddenly 4 new teeth popped through, including some molars! So they must have been making his mouth quite sensitive. He's just started eating/chewing properly again in the last couple of weeks.
If she really doesn't eat well for awhile, despite the tough love approach (it didn't work here either) then perhaps purée servings of your dinner instead. That way it's healthier for her, but you aren't cooking two meals either.