You MUST get evidence of this. Get video and photo evidence. This is malicious damage with intent. You are entitled collect evidence to this type of behaviour. Make sure you do NOT record anything going on INSIDE her house.
Your neighbour is a solicitor. She CANNOT plead ignorance, not that is a legal defence anyway. BTW, she has already gone the legal route and lost on both occasions - planning objection and appeal to an Bord Planala, so she is trying to circumvent the process.
Once you have the video/photo evidence, notify the Council water dept. that this is happening and ask for an inspector to visit BOTH properties, yours first.
Get your builder to bill for everything arising from the flooding, damage to materials, rework, lost time etc. Send her a copy of the bill, seeking recompence. If the bill isn't too high, you might be able to take a small claims court case - not sure if it will take on a case against a third party(?? Anyone).
Get your builder to dig a soak hole and pump out from it - this will go a long way towards alleviating the flooding problem - AND bill 'yer woman' for the pump hire and extra work.
Do NOT get involved in 'tit-for-tat' nuisance games, e.g. noise etc - drags YOU down to her level and WILL go against you if you have to go down the legal route - and you may have to do that, in spite of everything.
This is Bullying. And I hate bullying...stand up to her.
FWIW, given that she objected to the planning and appealed - and lost both, armed with video/photo evidence, a statement from your builder, a written compaint to the council and complaint to the Gardai, I think that YOUR solicitor would have a field day with her. She has NOT got a leg to stand on - so kick them out from under her! TODAY!
btw, write EVERYTHING down!