My vet has recommended pulling the baby teeth out if they are still in by 7 months to avoid any negative effects on the bite. I think it all depends on the dog, where the baby teeth are located and what their starting to throw off. One of my girls didn;t have her last two baby teeth extracted until she was 9 months of age and it was affecting her bite at the time...but her bite shifted back to perfect within a couple months after that.
Sometimes you can help those baby teeth come out by themselves by wiggling them. I did this for my Bailey. She had 2 baby teeth remaining at just under 7 months. They both came out after about 2 weeks of my wiggling around
How old is your Mia? Your vet can give you a better recommendation based on what he or she sees in her mouth.