I assume that Sofia would be the beneficiary to Mark's money, not Callie. She might have been Mark's proxy on behalf of Sofia but since she was never his spouse she herself would not get the money. I guess what I am ultimately getting at is, Callie would have to at the very least consult Arizona before "rallying the troops" because Arizona was the one that received the money and since Arizona is Sofia's other mother, which I assume legally, Callie technically only has 50% of input of where Sofia's $15 million goes (assuming she and Arizona could even uses Sofia's portion and again assuming that Sofia and whoever is Lexie's beneficiary received a settlement).
I don't think that Callie and Arizona are legally married in Washington State. Gay marriage wasn't legalized until December 2012, and they were "married" before then (AFAICT, they didn't leave WA to get married). And I don't think Arizona is a legal parent to Sofia for the same reason. So Callie is acting for Sofia, her minor child, as the benificiary of Mark's estate.