she now sayes she is going to sue me because i never said i was going to clean her windows this way
It sounds like a 'SEP' (Somebody Elses Problem) to me (hers). It's certainly not yours; although I doubt you'll ever receive payment for the job.
As a rule, windows and doors are designed to keep out the rain. Fact.
It's not your fault that this lady has let her property fall into such a state of disrepair that they leak when you cleaned her windows; with a WFP;
in accordance with the current Working at Height regulations.
Tell her you'll see her in court. It won't come to anything; you probably already know that.
Not only that, a bit of water won't really damage her carpets (the carpet cleaning lads may know better). Did it touch anything electrical or photos or anything?
I do a couple with cracked windows that leak or dodgy doors. I try to be carefull with how much water I'm pumping round the crack, but if they leak; tough.
They should get them fixed.
Why should I take the time to get my ladders; therefore lose money; when they should get their windows fixed in the first instance.
I've had no complaints so far mind; but that's my stance.