Puppy ear infection?

Hi,

I adopted a toy fox terrier mix about two weeks ago from the pound. They estimate she's 3-4 months old. She seemed healthy and happy and is up-to-date on her shots. She's a sweet dog and I love her to death. When I first got her, she had floppy ears.

Well, Nala and I left for vacation a few days ago and while we've been away from home, her ears have gone up. I suddenly noticed what looks like a serious ear infection! I feel bad that I didn't notice before and I made an appointment with our Vet for when we return home on Friday. I've done some research and it looks like maybe ear mites? She has also been shaking her head a lot. I'd really appreciate some advice. Thank you for any help.