(pennsylvania) Landlord Went To Magistrate For Spike In Water Bill.

Location: [PA] Former landlord is taking me to magistrate over a $5K plus water bill. What are my rights?

I’m located in Pennsylvania, and I’m looking for advice because I’ve never dealt with anything like this before. I believe our toilet may have been running without us realizing it, but we were unaware of the issue at the time. The biggest complication is we shared a water meter with the upstairs neighbors. The meter is located in the basement, and both apartments water usage goes through it. Water and gas were included in rent, and in landlords name. The landlord showed us a water bill that was over $5,000 and past due. She called us frantic on phone. She later got accepted into a water forgiveness program based on a plumber’s report when they came to check what caused it. They accused us of being negligent tenants and initially told us we had 90–100 days to leave. They then took that back and presented us with a new lease that included a payment plan asking us to repay $1,300 toward the water bill. Then rewrote it and said actually $1,400. Then a third time of $1800. They kept rewriting the lease and when we wouldn’t respond they eventually asked for a payment plan of $800 plus. In text they also said that we had stopped the leak in time, which makes the situation even more confusing. Our lease was month-to-month and the time we lived there they already increased rent twice explaining that it’s due to water bill being high. We still signed those leases in past. October was our last straw to leave because something seems off and I’m not comfortable paying a water payment plan I don’t have proof I caused. I asked to provide the actual water bill and explain how its determined what portion of the bill was caused by us versus the upstairs neighbors. However, because we shared a meter, I don’t understand exactly how much water we used. Now they’re taking us to magistrate court, and I’m genuinely scared because I’ve never been through anything like this.

Can a landlord legally make tenants responsible for a water bill when water is included in the rent and the meter is shared?
Does she have to prove how much of the $5,000 plus bill was actually caused by us?
Can she hold us responsible for $1,800 without providing an itemized bill or proof? I’m freaking out.