Your daughter could be sick or she could be entering what is a fairly common phase from about 18 months or so onwards (excersising control over the food they eat).  My daughter ate everyithing EVERYTHING until she was about 18 months when she suddenly stopped.  Now she would probably eat weetbix pasta, bread and potato but picks at everything else.  She rejects vegetables now and fruit.  I had to decide whether I was going to force feed her (not a good idea I thought) or supplement her diet with vitamins.  I chose the latter of course.  It's terrifying for a parent when their child just switches off healthy food.  I think all you can do is continue to dish it up and continue to eat it yourself in front of her and just hope that the phase doesn't last.  Disguise some vegetables in whatever food she will eat.  Very hard to do with yogurt but the refusal to eat all food except one type will definately end soon.  The problems with food in general, however, will probably persist. Like everything abuot little ones though, everything seems to occur in stages and nothing lasts forever.  

honestly, i think its a phase.. i remember my daughter and son going through the same thing.. eating all kinds of things and then suddenly wanting nothing but the same thing all the time.. they would be like that for about a week or so. and then change to something else.. i figured that over the course of time the were getting the variety they needed so i didnt worry too much..i remember thinking once that my daughter would turn into an apple if she ate anymore..lol.. cuz it was a REAL struggle to get her to eat anything but apples.. just keep perservering. keep offering up regular stuff.. she'll get back to eating it.. xoxo

Sometimes you can't tell when they are teething. It could be that or just a phase she's going through. Mine did this with eating but with her bottle, it almost drove me crazy. But it only lasted 2 weeks and she is back to normal now. good luck.

If she seems OK otherwise, I'd say it's just a phase and don't worry too much.

My son is normally surprisingly good at eating just about anything you give him.  But he goes through phases where he won't eat anything but rice krispies and plain noodles.

I've read up on this a bit, and I've heard that during a growth spurt eating habits will change, for example, a child will eat like crazy a few days before a growth spurt, and then eat hardly anything while the growing is actually going on (DC's routine).

I've got him some toddler formula for those 'not eating' days, just to make me feel better.