To me it seems it is just over, stop worrying…
I never had a legal case here in Taiwan, but I spent 15 years in China.
I got several traffic accidents there, with me being totally innocent in some cases, to being the cause of all in others.
I mean I have been sitting on both side of the table.
In China (and I think the same procedures are going on here), the police station and its officers have a much bigger role in solving matters, and preventing them from going further into the legal system.
After the report, they try to mediate between parties, try to get both parties find a solution, then let both parties make the contract and sign.
Simply said, if parties agree (whatever the solution), the agreement is legally binding, and prevents any of the other parties to seek further legal action in a later stage.
Once signed, it is over!
In your case, you have signed the agreement in the police station, and you paid.
I do think the shop-owner wanted to keep pressure on you, but I can not see what kind of paper she should come up with after your agreement.
Now, as I said, I think your case is just over.
The shop has other things to deal with, the police will not take action for something like this, and you learned your lesson.
Now, take a deep breath, go out, look at the blue sky and start living again!