Yes, you seem to have opened your home with good intentions and this person is taking advantage of you. What makes you responsible for them? Don't wait, remind the guest of your rules. You are the master there, and can change the rules as you wish too! Don't give them another day of rule breaking, you can't afford that, imo.

If they don't agree, then have them leave in the morning (they will only find another person to freeload upon.) Remind them that they can't come back, even with a promise because they didn't keep it this time. Urge them to get help with their problem, but wipe the dust off your feet on this one. Take care of you... I'm sure it was hard work for you to get where you are, don't allow someone to risk your health.