I agree with Jaysee (often
). Goldfish produce large amounts of waste and can get very big. The fancy goldfish grow to around a foot, and the non-fancy varieties grow maybe twice as big. Comets are very fast swimmers and need a lot of horizontal swim space. I think the minimum tank those three fish should be kept in is a 70 gallon, and I think that most fishkeepers would say even bigger.
Your friend should strongly consider rehoming the fish. People have probably told her that a goldfish will only grow as big as its tank, and while this is (sort of) true, it is not good for the fish. Their growth is stunted, and this is very harmful.
No matter what, she's going to have trouble keeping the water parameters safe for the fish. They will produce so much waste that, IMO, even if she did very frequent water changes, she wouldn't be able to keep up. They are going to continue to be exposed to ammonia, eventually leading to death (a goldfish can live 25 years in appropriate conditions).