A cat is probably not the best pet to go for if she's being impulsive, tbh no pet is best to get if it's an impulsive buy, but at least a hamster is in its cage an won't cost £20 for a bag of food or cost hundreds to be boarded when she goes on holiday, an although hamsters should be handled daily they are also fine with limited social interactions (the older mines gets the more he gets grumpy about being handled lol he's a proper old dude now an just wants his quiet) but there's A LOT to think about when getting a cat (or any pet for that matter) an boarding can be massively costly, am not sure much on cat prices but our dog was £300 for two weeks
She would also need to think on if she's going be able to handle a kitten, my mate had almost lost her patience with her cat when it was young because it was absolutely mental, not all kittens are going be calm, she loves her cat now but it was a difficult time for her when it was a kitten an she's had cats for years an really struggled with this one, so is she going be able to handle it if it's energetic? Or even if it had health issues? Or has allergies an requires specialised food? Not all cats can just eat whatever as well, you don't know till they are a bit older if they have allergies an specialist food is not cheap, my mate is $50 per bag because her cats has allergies