this is something that is happening more often than one thinks. My wife recently got lured into a "get rich quick" crypto scam scheme. They get you to deposit money, then download an app and simply show that balance continually increasing in that app, if you get greedy you deposit more money. Boom! suddenly one day these guy just stop.
So your wife just deposited the money into a random app which shows you increasing money without any sort of proofs for the profits ?
I doubt you or your wife checked for users who had successfully withdrawn money from that app.
How can one literally trust an app in this generation where people don't even trust their blood relatives.