The lengths some people will go to for a nostalgia fap.
Weird thing is I remember this movie but only in the part about seducing the stable boy and framing him for rape. I've seen 1000's of films so have no idea. Decided to do a little google of 'frames stable boy for rape movie' and the second search result appears to be you from 2011 but with some of the naughty words (and clear target for wanting to see the film ) removed for the OCUK edit.
Good luck!
Come on OP, is that it?
I suspect the OP is rather busy currently.
http://m.imdb.com/title/tt0234890/
This seems to match a lot of what is in your description. Housekeeper seduces father and son whilst messing with the wife's insulin, and encourages the daughter to put it about.
There's also a shower scene and a pool scene and a dramatic looking finale in the rain.
You didn't think it was gonna be that easy, did you?
In which country was the film set? Approximately what year was it made?