Welcome to the forum, KittyCatKatie!
Simple solutions will be the order of the day, then.
Before that, though, a couple of thoughts for you. I would be more than usually concerned because the discharge is yellow - to me, that says there's a bacterial infection going on - usually, with "colds", it's clear.
Now, the Baytril you have (which you shouldn't really have at all - antibiotics should be used for the entire course of their prescribing, and, not doing that can result in the infection lingering "quietly" only to flare up again) - personally, I wouldn't use it for many reasons.
What I would do, based on the personal circumstances you've described, is to call the Vet who advised using the L-lysine and do whatever it takes to speak with her/him personally - it will probably mean a call-back. I'd remind him about Katie, her age, the L-lysine...and I'd tell him about the yellow mucus - then, about my financial crunch, and I would ask her/him for some consideration in light of my circumstances - perhaps suggest that you could pay something and the balance in a few weeks.....
There are a number of problems with using the remaining Baytril: it may not be the "right" drug for this bacteria, so it might only "mask" what's really going on...you may not have enough to eradicate the problem...etc.
Keep a sharp eye on the amount of food she's eating - if it slackens, you may need to assist-feed her. Post again if this is happening - and don't "wait-and-see". Cats can develop a serious liver disease when they don't take in the amount they need.
For those home remedies...the L-lysine is number one. You can give 500mg twice a day.
The humidifier is something I use when one of mine is having an episode and I know it helps. You could also give her a more intense dose by running a hot shower to create a "sauna" effect and staying in there with her for +/- 20 minutes at a time.
That "steaming" treatment can be done another way - and you can use a simple-ingredient nasal drop too - both of these are described right here
http://www.harpsie.com/cat_flu.htm#steaming Those drops should only contain buffered sterile saline, and only be used for 3 days.
I hope some of this may help - I'd really urge you to speak with that Vet, though...the fact that s/he recommended L-lysine tells me s/he knows a thing-or-two about cats - and, would hopefully have the compassion to see her.
Please keep us posted!