im getting her a 3g tank, and i was just gonna get her a betta, but mom told me today how ugly she thinks they are and that they are the most useless fish shes ever seen
Bettas are about the only thing you can keep there. Anything smaller than a 10g are just novelty items not meant to properly house any fish IMO. Why not get her a 15g instead? You'll find the nano tanks are ridiculously more expensive than the larger ones as these are novelty items.