There's no way to be profitable with this pricing. Simply no way. Each time an user opens the app it will cost 2 cents in API requests. Continue scrolling, open threads and the costs rises. In average, accounting all the lurkers, inactive and free users, it might look like that it could be supported by a $2 subscription. But then, who is willing to subscribe to an app to read a free website? Only the most addicted users. The ones that will doom scroll for hours. The ones that will do 10000 api requests per day
Also, the server backend must be rewritten from scratch. Right now the app is open source and it's talking directly to the reddit servers using the API key. After the change, it could continue to do so, but because extracting the API key from the APK is trivial, some asshole could extract/crack it and give her a massive bill
Every single request must be proxied by her own server, making a check for a valid subscription to each user and also some quota management. Possibly some caching to save money on the most popular posts. Otherwise it will be trivial for some asshole to make a revanced patch to bypass the subscription. But implement this takes months, she can't have done this and tested carefully in just two weeks
Please someone let her realize this before she gets a massive bill at the end of the month, i don't have a reddit account for that