Here is an article with the life cycle of a flu:
http://www.parents.com/baby/health/sick-baby/babys-first-cold--flu-season/
Typically, when the mucus is yellowish or crusty, the cold is about to have ran its course. My cousin usually only gives the medication when baby is still having runny nose and stop once it goes into the middle phase. Breastfeeding would definitely help strengthen the baby’s immunity. That being said, her body is still developing and building her immune system, exposure to the outdoor elements and other environmental factors will still make her vulnerable to various virus, bacteria or infection.
Hope she feels better soon!
Take care of yourself too mummy!
Anonymous