A question about theft arrest charges being dropped?

My little sister took some things from a store called Superstore, got caught and was arrested. But, because she has a clean record behind her, the police dropped the charges of under $5000 dollars that Superstore was asking for, but her name will be up in the air with the police if anything were to happen again. This is what she told me.
A month after the arrest, I received a mail from LobLaws (the company that owns Superstore and other grocery stores) and it stated that she is being charged $325 for her arrest that day. What I don’t understand is, if the police dropped the charges where is this fee coming from? She has 15 days to pay this or she’s taken to civil court. I asked my father and he told me that my sister should not pay it. He said that she did nothing wrong since the police dropped the charges. LobLaws is just trying to get money from her. If they plan to take her to court, they will contact the police and they will find nothing wrong since they dropped the charges that day? My father says that we should just ignore it.
I don’t quite understand what’s happening here. Should we just ignore this?

She should pay it…yes…

They are making a demand for the money it cost them because of her intentional tort against them. The criminal charges were dropped, but she still did cause the store to spend money because of her actions. If she doesn’t pay, they can sue her and win. A judgment will be on her credit report, etc….

It’s better to pay the $325…she got off light.