For food deliveries I tip a minimum of 20% or $5 flat for small/cheap orders to make it worth the drivers time.
EDIT: After actually READING the link (sorry) I have to say that the only "adjustment" I would have made in this case was reducing her tip to ZERO and I might well have called the cops if she didn't leave promptly.
I CERTAINLY wouldn't eat anything she touched under any circumstances either so taking the order with her is fine.... saves me chucking it in the trash.
If you have to rely on tips only if the company is not paying you enough then don't work for said company.
Working for doordash and all the others that scam their drives so much is only helping them get richer until people smarten up and actually go after them legally for not meeting minimal wage requirements.