I am sorry to hear your dog is having this problem.
The first thing to do would be to have her seen by a vet a soon as possible. Eye problems can escalate from a little bit red to loss of vision very quickly, it is always best to handle eye problems as soon as possible to avoid long term damage.
Glaucoma diagnosis requires testing the intraocular pressure (eye pressure). If the pressures are elevated, then drops are given twice daily to lower the pressure. This is how most glaucoma is treated. Some cases are more severe and require multiple eye drops, some require surgery (very rare).
Since we do not know if this is glaucoma, you should avoid any over the counter medications that could make this worse (ibuprofen, aspirin, etc). Your vet can give you appropriate safe pain medications for her condition dependent on the exam. Medications that increase risk of bleeding (like NSAIDs) can make eye problems worse depending on the specific diagnosis, so it is safest to wait. If you have tramadol or gabapentin that has been prescribed for her in the past, you can give that.
The best thing to do is have her seen this morning if possible to make sure they eye is not glaucomatous. There could be something else going on such as a corneal ulcer, conjunctivitis, or uveitis (inflammation in the eye), which can often look similar without testing.