Now I can either fix 2 ways:
1) Replacing the bottom panel with a different model panel (as these garage doors have been discontinued). Mismatched panels will likely reduce the value of the house.
2) Replace the entire garage door, which will cost a lot more.

Problem:
As landlord, I asked her to pay for the damage. She refuses, claiming that part of the accident was due to "normal wear and tear". She claims that on previous occasions, the garage door would not open completely and she would have to reclose/open it with her remote control.

The repairman who came to look at the garage did say the opener chain was loose and stretched out from use, and that this could cause the garage door to "stick" sometimes. I live in the house also, and have not noticed the garage door "stick" when I come and go.
I have also heard that garage doors tend to "stick" during snowstorms, so that could have occurred here.

My concern is this:
I believe she is responsible for 100% of the damages because she didn't watch where she was going and drove into the partly closed door.

She refuses to accept this, claiming that I am responsible for at least half of the damage since the garage door got stuck. I don't know why the garage door even got stuck-- whether it was the motor chain or the snowstorm.

Honestly, either way, I still think it is her fault for being negligent. She ought to cover the damages. Unfortunately she seems to be taking this very personally and deflecting blame from herself onto me.

Could someone please offer me advice on how to resolve this issue in the fairest way possible?

Thank you!