Insurance form asks for weight-is it wrong that I'm upset my wife won't tell me her weight to finish the form?

My company is attempting to switch insurance providers. On the form is a lot of medical history information, including weight. My wife refuses to tell me her weight for the purposes of this form.

I love my wife, have told her clearly many times that though I think we both should lose weight for health reasons, I think she's beautiful at any weight, and I will always love her.

When I told her I needed this number, she said "guess". This is a legal document, and knowingly putting inaccurate information into the form is insurance fraud (she says I'm being "unreasonable" and making this "more stressful than it needs to be", but I don't like fudging anything on legal forms especially when I know them to be validated against other documentation already out there).

So, am I right to be upset with her dragging her heels and wasting 4 hours of my workday fighting with me over this one number, or is she right to "keep this number private" even when I'm the one requesting it and need it for a legal document?