[WA] Stopping harassment by relative who is abusing APS

A very distant relative has come to learn that I have a successful business and sizable income. I met this relative ONCE in my life for a few minutes. I wasn't even aware of her full name without asking other relatives (those that will still talk to me at this point).

She has told other relatives I stole a bunch of money, and was going to sue me if I did not give her money. I have not had contact with this woman for years, and have never had access to anyone else's money. A few months later I get interviewed by APS regarding outlandish, and straight up false allegations. We know it was this lady, as she calls me by a name that is not my name (she doesnt know my name!), and APS addressed me the same way. Allegations that are not only over the top outlandish, but completely impossible (I was out of the country at the time, on the other side of the world, and proved that). After it was clear the allegations were blatantly false, my attorney asked what APS was going to do about the reporter using them as a tool of harassment. APS stated that it was not their responsibility to stop her from using them as a weapon to harass me, and they will investigate every allegation they receive.

My attorney only does CPS and custody cases (I found none in my area that specialized in APS, which is why I hired him). He has no recommendation at this time on how to stop this harassment.

The harassment is ruining my reputation, alienating me from family members, causing me to miss work, and racking up legal bills. APS accusations also put me at risk of being unable to accept some work contracts and participate in some youth and homeless programs i volunteer with (really important to me, as I was homeless at one point).

I have reached out to personal injury and civil attorneys to see if suing her might be the best route, but none thought it was worth the time or money and turned me down.

How do I legally stop her from alienating my from my family by spreading false allegations, and how do I stop her from using APS as a weapon to harass me? My biggest fear at this point is that she will move on to CPS to harass me, and I have small children. Is there a certain type of attorney I should look for?

I don't care about the cost, I just want her to stop, but I'm not willing to bow to extortion and pay her to leave me alone.