How to navigate past due utilities bills from Tenant?

[Vincent Plant]

I inherited a tenant on a property that I bought about a year ago. The property's sewer/water/trash bill comes in Quarterly from the borough it's in and the account is tied to the house. 

The lease I inherited states that when the bill comes in, landlord is to send a copy of the bill to the tenant and they are to pay it within 20 days or there is a $50 late fee. 

Typically my tenant would pay it, sometimes over the course of a few weeks but it worked out. Now, she has not paid it in months. She owes over $700 towards it and its backed up to June. She is paying the rent in full each month, but she says due to covid she can't pay the utility bill and she is trying to apply for assistance with her utility bills for covid relief. I have applied the late fee and given her formal notices but she just keeps saying "I'll take the late fee, I can't pay it right now, I'm applying for assistance which I should have soon." 

In PA there is an eviction moratorium until the end of the year. I feel like I don't have much control over this situation. The only thing I can think to do is document everything with email notices to her, and possibly begin deducting it out of her security deposit, which I'm not sure if I'm even allowed to do. 

Any suggestions?