No top teeth

My rat, Demeter, doesn't have top teeth. I have taken her to the vet and he said she should be fine...but she's not. She has a harder time eating and she is losing weight. I have tried hard boil eggs for protein but she doesn't like them. Please help. The vet isn't much help. I don't want to lose my baby because I can't help her. If anyone could help me with maybe a diet I can put her on.
My other rat, Persephone, is perfectly healthy and active.
As for the top teeth, I have been to the vet three times because her bottom teeth overgrow. He said it's rare but her top teeth haven't come back.

What kind of food are you feeding her? If you have a lab block like Harlan or Oxbow you can add some water to it and turn it into mush. Worse comes to worse you can syringe feed her the lab block mush too.

I originally did a care fresh grain mix, I switched to blocks a couple days ago. She can eat the smaller pieces of grain mix, it's not helping her. I'm going to try that with the new block food. Thank you for the quick reply.

Hi! Rats' teeth keep growing their entire lives (incisors). They keep them short by chewing things and bruxing (grinding their teeth). If she is missing her top teeth, she will always need tooth trims, usually every two to three weeks. If her teeth are allowed to overgrow, she will not be able to eat because it will be too painful - her bottom teeth will poke into her gums on the roof of her mouth.
So first off, make sure her teeth are trimmed on a regular basis. Then buy a high quality food like Harlan 2014 and soak the blocks in water so they break down and then pour off the excess water. This way she can eat them without having to chew them up. I usually get a couple of small flat-bottomed dishes and have one in the cage already soaked and one in the fridge soaking, and change them morning and night. You will have to do this for the rest of her life.
Your vet does not sound very smart about rats. Is there another, more experienced vet you could go to? And don't let them try and talk you into extractions for the overgrown lower teeth as it is a very difficult surgery and only as a last resort.

Where do you live? How old is your rat? Has she always not had her top teeth or did she suddenly loose them?

If you can get them, Oxbow blocks are really easy to soak and soften. That's what I fed when I had a rat that had incisor issues and she loved it.

ETA: I got sidetracked while writing this reply and Joanne posted a lot of what I wanted to say.

Joanne covered it all, but I want to add that I have a boy here whose top teeth fell out a long time ago, and he's surviving very well on lab block mush. I use mazuri or harlan blocks put it in a small tupperware container, add water so its well over the blocks and let it sit a couple of hours. I also had a boy who had all his teeth do well on this twice a day lab block mush feeding...he's a bit chubby Bean's bottom teeth are growing towards each other so aren't overgrowing like your lady's, but if they weren't I would be looking at having them trimmed every 2-4 weeks depending on growth.

Good luck with your baby!

As said, you should find a very rat-savvy vet, as you may need your rattie "operated" on every few weeks to trim his leftover teeth. Where are you located?

Baby foods / cereals are great to use too.