Hank, you really didn't give us quite enough information to help you. It could be anything from a respiratory problem to nothing at all. Keep in mind that
all cattle would have snotty noses
all of the time if it wasn't for grooming their nostrils with their tongues.
When you first noticed it on Monday, had the heifer just gotten up or had she been active? Is it clear or green? Does she have a good appetite? Does she appear full or gaunt? Depressed or lethargic? Holding her head lower than normal? Cough? Rattle when she breathes? Eyes watering? I assume you haven't checked her temperature?
Here's a link that might help you some more:
http://ianrpubs.unl.edu/beef/g1179.htm