Shared box gutter

parent13

Hi so got a shared box gutter which runs the length of the roof between nextdoor and myself.  Its lead and been leaking for years.  Approached the neighbour several times and is not cooperative and willing to pay towards the cost of replacing this.  Refuses to acknowledge she has a shared responsibility.  So for the last few years we have had it painted with something to keep it from leaking which is a temporary thing.  Last year it leaked again into my bedroom.   Approached next door for the roofer who done her roof (since this has been leaking) and she said it must be sorted and gave me his number.  He advised to get it done this year when weather is good.  So told neighbour who once again does not want to pay for it.  So booked roofer and his scaffolding team came and erected the scaffolding which is overhanging on to her property at second floor  height.  Obviously has to be like this for safety as the box gutter is in the middle.  She has now sent me a nasty letter saying she has got legal advice and that this is encroaching on her property and that she wants it removed.  I have knocked and tried to explain that this is for the benefit of both properties, that she even gave me the roofers number and agreed last year.  I have also pointed out again that she should be paying towards this and that we are paying her share and that its benefiting both properties, it needs doing and we have maintained it for several years at our cost.  We accept that she refuses to pay.  

Its getting done tomorrow.  Where do I stand and what are peoples advice please.