Nobody should be trusting Google or Apple to be protecting them. Certainly not for a $1M+ USD deposit.
That the app stores are illegal monopolies shouldn't opine on someone suffering the consequences for their own poor decisions.
I agree with you, I wouldn't give someone 10 euros if not vetting, but if google puts "Verified by Play Protect" , restrict me to do anything, talk about their stores as a safe and vetted place, then it must be kept accountable
1. Dealing with Google's failure to remove in a timely manner
2. Dealing with the fraud
Comingling them creates a slippery slope ("I drove my car into a lake because Maps told me to...") that erodes normal expectations of personal responsibility.
What should she have done to vet?
Go to the website of the party she's transferring the money to and verify the app from their end?
That doesn't seem much to expect for a multi-million dollar personal risk.