food issue with dog in heat?

Yes, a heat can put her off her food. She may just seem generally out of sorts and clingy, especially if this is her first heat.

If you have any other dogs, watch for status challenges between this pup and any other females you own, too. If you have unneutered males, they obviously need to be carefully and faithfully separated. Double barriers are best in this case.

You also need to restrict her to leash walks in your yard ONLY to minimize the chance that any males will try to breed her while she's outside.

The food that I fed my German Shepherd Dog pup was a dry food for puppies because a good puppy food will have what he needs to grow. I do not know about your dog but mine doesn't reach maturity till age of two, that's when he has reached full growth. He is on a high end dog food now that contains no grains. You can ask your vet about this or better yet have your Mother ask. I am sorry that your previous friend got hit. You do realize that you should be training your new friend now right? Also some people food even given only as treats can cause problems like diarrhea so best to stay away from it altogether.

Its possible. Add some boiled chicken or beef on top of her food and see how she does with that. Toy dogs are notorious for being fussy and "living on air"

Talk to your vet about it. THEY would know best for her and have a better idea of why she's not eating.