The red discharge is called porphyrin and is a product of their Harderian gland. The presence of it does not, to me, indicate the need for an immediate vet visit. It can be an indication of illness but also it can indicate a stress reaction.

Gently wash the rat's face with a warm, wet and soft wash cloth over the next couple of days to make her more comfortable. Examine the eye area to see if there's any physical issues you can see (bedding in her eye, etc.) Determine whether she and her enclosure mates are on the whole healthy (check for things like breathing, sneezing, loose stool, etc.). Make sure this rat is not being stressed by being overly dominated by a cage mate.

Make adjustments to any issues you find that may be contributing to the presence of the discharge. If you see any reason, however, to suspect an illness or injury to the rat, of course, see your vet if that is the appropriate choice for this rat.

Watch her closely otherwise to see if the discharge goes away after some changes are made that may be causing it in the first place.