(Colorado) Apartment complex is screwing me out of money

I took over a sublease in September. Last month my apartment bill was about $100 higher than it should have been. I went to the front office, told them the mistake, and they said they would get back to me about the correct amount (Because of water and utilities it's not always clear on how much I actually owe). The extra amount was due to an outstanding charge from the previous tenant. I never heard back and I had a flight early the next morning, so I decided to just pay the full amount they charged and let them correct it for the next month so I wouldn't get a late fee.

I contact them again and they tell me: "Basically, what I found out is that since you have already paid the amount, we are unable to contact (person I took over the lease from) and demand that payment.

We are not legally allowed to “double charge,” so you would personally have to reach out to (that person) and sort out an agreement."

This is a person I met through Craigslist and I have no recourse to demand payment from her.

The apartment complex's online billing system is terrible; I actually have access to the previous tenant's saved billing information since they never bothered to make a new account for me or erase it.

I'm considering 3 options:

1. Pay the full amount just because I don't want to get evicted

2. Only pay them what I agreed to pay in the lease. This would mean I'm short on this month's payment and they can charge me a late fee and possibly more. The lease ends soon.

3. Pay what I agreed to pay in the lease, and charge the extra to the previous tenant's bank account.

I'm really not in a financial situation where I can afford to just give away money, but I also don't want to get in legal trouble for #2 or 3. Any advice would be greatly appreciated.