Why the hell won't my kid sit up?

I know every baby is different (this is one of my favourite lines to use when someone asks why their child isn't hitting a certain milestone) and she will eventually do it, but I'm perplexed as to why darling daughter won't sit up. It isn't because she can't. It is a flat out I don't wanna attitude on her part. When you try to put her in the sitting position, her back gets rigid before she starts to recline towards the floor. Yeah, life would be easier if she could sit up, but sometimes darling daughter doesn't want to make her mother's life easier.

I was okay with her not sitting up until today. All the babies at today's playdate could sit up. Even a five month old at a playdate last week could sit up. Darling daughter has at least two months on this kid and the younger baby could sit up without any assistance. My kid? Well, she just kind of slides onto her side when she decides not to make her back go rigid.

Today I learned from Ottawa Public Health that I've got four weeks, FOUR WEEKS, to get my kid to sit up. Well, it isn't the end of the world if she doesn't sit up before she turns nine months, but it is one of those milestones she should conquor before she turns nine months. According to the public health representative I spoke to today, it should only take her a week, with the help of practice, to get the hang of it. Practice or no practice, I don't know if she will be able to do this. But all I know I have four weeks to get to sit up. I'll keep you posted on what happens.