Aww lookit the little baby!
The anal and tail definitely do not look like a betta. Somehow your sister ended up with another baby fish.
If you can take a closer picture just to be sure- so we can see the anal fin, would be nice. But if the tail has that < curve in it, and the anal fin isn't elongated the length of the bottom, as well as lack of camo stripes- then I would have to agree, it's not a baby betta. But that is just my opinion..