How can I help her tonight? Cat with viral upper respiratory infection.

You can warm her food when you feed her, since her sense of smell is
diminished right now. You can also turn on your shower to super hot
and close the bathroom door to create a steamy room. Let her stay in
there and breathe in the moist air (only do this if she doesn't have
allergies or asthma, or you could cause a flare up).

The l-lysine will help too. If you have access to it locally, there is
a flavored gel available called Viralys.

Give her lots of comfy sleeping places and plenty of cuddles.