I'm no expert, and while it does look like her signature that doesn't always mean much. I will caution that a few of these Black Canary pops that I have seen from sellers associated to RACC and with authentication of the signature(take that for what it's worth) all have one thing in common - Katie's autograph and "Black Canary" which she has written on it as well.
Look more at who the person is selling it. Are they a seller/dealer of autographs or just an individual who met Katie and is now selling this pop? Do they have any authentication or just their word?