Keeping sick baby hydrated

LO will be seven months on Thursday and has her first cold. She's been nursing for just a couple minutes at a time and just not drinking much at all. She's having wet diapers so she's not dehydrated but I'm needing advice for how to keep her that way, and other than diapers, what else to look for. I know they say their soft spot will be sunken, but how obvious is that since it's covered in hair??