This is a legal issue and not one that we as Realtors and without more specific information about your lease agreement. I suggest that you contact a real estate attorney to help you sort this out. Your solutions should be according the law, your lease, adn the advice you obtain from legal council. Not from the pressure and insistence from the 'friend of your parents'.
Your Castle Realestate
Pre-existing issues with windows would typically not be your responsibility to fix, UNLESS you had identified a problem, not let the owner know of the problem, and by continuing to use the damaged window incurred additional damage as a result. Keep in mind that I don't know the exact details of your situation, and we are not attorneys, so it's really hard for us to comment on who would ultimately be liable for fixing what.
I have seen this situation play out time and time again - so, not to "lecture" you, but the lesson learned here is to be ultra dilligent when documenting the move-in condition of the home initially. Take pictures of everything, open and shut doors/windows, turn everything on and off, go over the place with a fine tooth comb, and document, document, document - even if it seems silly or unimportant. Make sure everyone involved is aware of all issues, and the condition report is signed prior to move in. It's better to "go overboard" initially, then have to argue with a landlord/owner after the fact.
I would first sit down with the owner calmly and explain the situation. If she refuses to compromise with you - and does ultimately take legal action - I would consult an attorney in your area on how to proceed.
My personal opinion however is, if it's just a few latches on the window, I can't really see how you would end up in court over it. Surely, you both can come to some sort of agreement for the repair and move on with your lives...
Hope this helps!
Additionally, consider requesting in writing, specifically what they expect of you with regards to these repairs. Ask for specific concerns so that you can either correct them before moving or respond as to why you feel the repair request is unjust.
Photographs, repair receipts, contractor estimates, etc. may come in handy should this be taken to the next level. Do what you need to do to be considered responsible but you shouldn't be expected to leave the property in better condition than it was when you moved in.