My daughter cheeks become fire truck red and become very hot even if shes cold, happy nothing triggers it. Shes 8 months old and in perfect health?

Probably fine. Some children get very rosy cheeks. If she's active fine, drinking fine, peeing and pooping fine, then she's fine.
Allergic reaction? If the redness is symmetrical and limited to both cheeks, it is probably benign. Sometimes food allergies can cause bright red cheeks...Just see if there is a pattern to the development of the redness.