It sounds as though you may have a compatibility issue at play in the species she is keeping - the striped fish could be anything from a danio to a tetra (ie neon, cardinal, glowlight) -- what color(s) was the striped fish? It also sounds like you are feeding all of the fish the same food - goldfish diet - while you actually have some small tropical fish.
Your reference to the "smaller bowl" would imply that they are normally kept in a larger bowl, rather than an actual tank - is that the case? Is the normal habitat filtered? What is the water volume of their normal habitat? How long has she had the fish?
There are a lot of possible factors at play here.
Goldfish are notoriously "dirty" fish - while they are commonly thought of as bowl fish, they are not - they are best kept in a well filtered habitat maintained by frequent partial water changes (30% or so on a weekly/bi-weekly basis). Honestly, very few of the common pet fish are "bowl" fish - a stagnant container of water is not going to remain healthy and supportive of good life. They, goldfish, also are "cold water" fish and do not make good tankmates for tropical fish who require higher water temperatures. While it is true that fish can survive in less than optimal keepings, the goal should be to have them all thrive by providing the best habitats you can (for comparison you might understand - a horse can survive if kept alone, in a stall and fed the absolute bare minimum of feed and water -- but to truly thrive the horse needs to be allowed turn-out, fed quality feed, offered good clean water and - best case scenario - provided appropriate companionship to fill their need for a "herd").
Knowing what species one is keeping is very important, as that is the only way to know what each fish's needs are - even withing the same grouping (ie tropical) there is a wide range of temperature, hardness, salinity, etc parameters that meet the needs of each species.
I would suggest finding a good LFS (Local Fish Store - this is not your local Walmart or big box pet shop - a good, local shop) where you are going to find staff that has years of experience and knowledge to share with you in identifying the remaining fish, educating you as to their needs and helping you to provide the best possible keeping for them and any other fish you might acquire.