Alright... so this is a pretty cute project and I definitely hope your sister keeps up with artsy things like this. She might be great one day! I think you should probably not put things like this on NG though. I think there's a rule against using sprites that aren't yours, which this video does.
Also, I really hope your sister isn't discouraged. Places like YouTube and Facebook would probably get the more positive reviews you're hoping for. There's an expectation on NG of professional or semi-competent animation, so projects like this won't be received well. I gave a low rating because this, compared to most stuff here, isn't very good. I do NOT hate it though, and I really honestly do hope no one is discouraged. It's not fair to compare stuff like this to the work of experienced animators, but that's going to happen here on NG. Best of luck to you and your sister! And the characters are really cute, she picked good outfits and hair colours for them!