What should I say to my coworker who wants to come in sick?

Nothing.

You’re not her boss. You’re her co-worker. Wear your mask. Pop an extra vitamin.

I’d let her deliver the supplies to the location and then pick them up when she leaves. There is no reason to spend a lot of time in close proximity with her.
Presumably you have lots of cleaning /sterilizing supplies. You might want to rub the containers down after she delivers the goods or wear gloves.

Have you considered that she really doesn’t want to bring you your supplies??? Maybe deep down inside she wants you to tell her to stay at home & take care of herself so she can tell her boss that you told her not to come in.

I’m a pretty straight forward person who calls it like I see it, I’d tell her that I don’t want what she has as I can’t afford to be sick & miss any work, so stay home & I’ll do my best to stretch my supplies for one more day. Then she & her boss can work it out.

Not your job. Take care of yourself.

The real question: Are you a bad person for not saying anything?

Say nothing.

If you can do without the supplies for another day tell her no. If you need the supplies, then ask her to wear a mask, wash her hands, and deliver them before you get there. You can wipe off the bottles with disinfectant to reduce your chance of catching anything.

Before covid I was careful about trying to not get sick. If you get sick you might not be able to work if it hits you harder than the other person. Plus, it could be covid. Covid comes up negative the first day or two all of the time. The positivity rate where I live is very high, like 18%.

If you are truly worried about her passing her germs on to her, keep your distance. If she is delivering supplies, she doesn’t have to hand them directly to you and give you a hug. She can put them down somewhere and you can get what you need later. If you are worried about her putting germs onto the packaging, take a wipe with you when you go to get your supplies.