That usually cures a bit of standing water in short order.As far as kicking her out or whatever over this - geez - some real tyrants on here.

Additionally, most leases address this issues and provide for cures should the unit become uninhabitable and allow for the tenant to break the lease after a certain period, and even if the lease doesn't contain a clause that says so, most states landlord tenant laws address this issue. 

If not post a 3 day notice to cure or quit and charge late fees. 

It is no different than any other tenant complaint , it is justified and according to the lease a landlords responsibility to cure.

For example, in Cali, to collect a late fee, you must provide a separate  three day cure or quit notice and cannot tack a late fee onto the pay or quit notice for late rent.If the tenant is on a month to month and paying late seems to be a pattern, consider giving tenant notice to not renew the tenancy and start with someone fresh.

Making exceptions not only causes issues like this, it can also be construed as discrimination or at least favoritism if your other tenants get wind of it, and they always do.This goes without saying:  issue notice to cure ASAP to let them know you intend to follow the contract you all signed.

2) Were your tenants ever issued any 3 day notices to pay or quit or cure or quit and what were the reasons?

Upfront communication and honesty is the best cure. 

If they owe you any money, you can probably file faster for that than you can a non-financial cure. 

Make sure to leave 24hrs between coats and it needs a week to fully cure.