30 fish in 4 gallon tank - help?

My frined has about 30 fish in a 4 gallon abk, She keeps it in her room. She has about 8 guppes, 10 tetra's, frogs, and so much more. I told her it is cruel but she just has a go at me. Her fish do die, but she does not see that it is crue. when i talk to her about it. she just says 'im not stuoid, its not cruel'. what should i do?