How do I say no

Vanessa

So my sister in law told me that she wanted to schedule me a 3D ultrasound whenever I turn 14 weeks and that she would pay for it & right now I told her that maybe by then we might be able to see the gender & she told me that yea but that she’s gonna keep it a secret to do a gender reveal but I don’t want one... and I feel bad telling her no, specially cause it’s her first nephew/niece ;/