My 9 month baby has a rash on her chest should we take her to the walk in clinic?

Depends. If your baby has a fever or is acting sick, she should be seen. If the rash is not bothering her and she doesn't have a fever it should be ok to wait. Howver, my general rule is that if you'll be up worrying tonight it's best to have your child seen.
Rash. If your infant is comfortable, not cranky nor has no fever, it maybe best just to monitor the rash as it may go away on its own. Now that it's summer, it can just be a heat rash which can be managed by just keeping your baby in a cool environment. Drooling may show irritation on the front of the chest - a bib will help prevent this. Fever and rash is a good reason to see the pediatrician.