advice regarding neighbours home insurance

[Deleted User]

i would like some advice please.
my neighbour died over a year ago and his elderly sister inherited the house. she lives a few hours away so hasnt been able to get there often and the house is in the process of being sold.Early April i noticed "mushrooms" growing along my skirting board on the wall that is against the neighbouring terraced house. On inspection it was rot and i ended up pulling off my skirting board and lifting a fair bit of my wooden flooring . i called the neighbour to see if they had a water leak and i could not see any issue in my house and have no pipes in that area, external wall and surrounding area was dry. The estate agent went in a reported no problem in their house. My insurance company would not come out to inspect the problem due to lockdown. I researched online and just dried the area out as advised.
Fast forward over 2 months and i am still getting small mushrooms growing. The online advice is that there must be a cause and it was likely a leak. I looked through next doors window (with permission as ive been helping keep their grass cut) and could see their house had numerous huge mushrooms and an obvious bad problem.My insurance company had told me they would be out in the next couple of weeks.
Now the neighbours estate agent has said the problem is their house and has a builder going in this week to inspect the exact problem. The house contracts were due to be signed with the new buyer this week. The neighbour has told me over the phone that she will likely pay for the repairs herself in both her house and mine, rather than the insurance as it will take too long and she just wants the house sold as its a stress for her. I am awaiting to hear if the house sale is still going ahead. 
As the problem is not caused by me i dont think i want my insurance company to deal with it.
My question is- where do i stand? am i foolish to take her word for it that she will pay for repairs? is there a correct way to go about this that protects me? If the new buyers go ahead with the sale will that impact on me?
We have always been amicable and i have no reason to not believe she will pay up ,however other than her first name i know little about her.
id appreciate advice. thanks