My question involves landlord-tenant law in the State of: CA

This tenant has problems in getting her pay for taking care of elderly clients which comes through an agency. The lease says

"Tenant agrees to pay a penalty of $5 per day late (rent becomes late after the 5th of the month). If rent is not paid by the 15th of the month, Owner may at any time after that, at her discretion, deliver a demand to surrender the premises immediately. "

However because I felt sorry for her I did not enforce the penalty when she started paying part of the rent and then the other part. It went then to three payments, and finally as you might expect she didn't pay all the rent by the end of the month.

Have I forfeited my rights to enforce the terms of the lease? I am concerned about this person who can't even manage rent of $675 a month becoming completely dependent on me. I am not that rich. I actually live off of the rent that she pays. In addition, having to worry about collecting all month long is causing me problems.

She has convinced herself that if she pays the rent by the end of the month she is ok. I don't feel that way about it.

Unfortunately, though, no records were kept of what she paid when, so I couldn't prove it.

The lease also says
"This is a month-to-month agreement. Owner may reclaim Premises for her own use at any time, after giving Tenant two-months' notice of her intention to do so. Tenant is requested to give 30 days’ notice of intention to leave." I have been thinking of moving back into that unit. Could this be an alternative solution?