Neighbours Roof repair causes leak

I'm looking for some advise for what I consider a dificult situation.

My neighbour had some work undertaken on the flat roof above one of her bedrooms as it had been leaking water in to the room for some time.

Since her "roofer" has completed his work, when it rains I now have water leaking in to my bedroom and running down the ajoining wall.

I approached her and she advised me that I should get my roofer in to take a look.

My roofer did indeed take a look and sent me photos of the work that had been undertaken on the roof. I paid to have the poor work where my neighbours roof joins my own roof to be redone. My neighbours roofer had used decent quality materials, but just hadnt finished the job properly.

Having just spent a weekend away I returned to water entering my bedroom again. My roofer assures me that my roof is sound, and so will have to look at tracing the water entry point and try and resolve that.

While I quietly hope that my neighbours walls are soaking wet like my own, I'm also fuming that I am paying to put right shoddy work by my neighbours tradesman. My neigbhour hasnt been forthcoming with the name of her roofer.

Has anyone been in this situation, how did / do you handle it?

It's looking right now that I will not only be funding the roof repairs but also redecorating my bedroom. Money I hadn't intended to spend.

My neighbour meanwhile seems to be avoiding me rather obviously on occasions.