Deceased father's girlfriend "hijacked" his celebration of life event

Location: WA State

​

My recently deceased father's girlfriend has decided SHE will handle his final event, and is fully alienating me (his oldest heir and legally appointed representative) from meaningfully participating. For instance, knowing my husband and I were having surgery, she kept making dates, forcing me to beg her to give me more time; she refuses to have it at a waterfront venue I reserved, instead, insisting it will be at her trailer home club house; she has retained the support of three of my most toxic/for will addicted/etc family members, people that I refuse near me because of their history of goofy ass behavior, that extended into the hospital as my father lay dying.

I have offered to share the responsibility with HER. But I set a boundary with my exposure to them, because it always ends up in attack, she insists they be given an elevated role.

I'm at a loss. I'm heartbroken my father is gone, and I recently lost my mother, where the same family members pulled the same dramatic garbage that I want to shield myself from. Do I have any recourse here? She went through his phone and has already contacted his friends, and invited me to have my own event-where my family and his friends would not be present. I dont want to tell anyone (including my extended family) what is going on, because frankly, this is a shameful nightmare. She only knew him for 8 years. He was in his 80s. Can anyone just decide when a persons Celebration of Life will be, and totally run over his heir and legal appointee?

​