How big is the tank? You could get a bett fish...You will need at least a 2.5 gallon tank with a heater and filter. Another idea would be to ask her what kind of fish she wants, then you do the research and find out what it needs. Lots of fish die because people do not do research and give the unsuitable homes. I.E. goldfish and bettas in bowls. If you have a 10 gallon tank you could get some platies or guppies. Beware though! They have fry like crazy. Hope I helped!!