Is this a silly way to start a personal statement?

I would say don’t explicitly say that it was that film, but you can say it in a roundabout way like ‘seeing the profession of law depicted in the entertainment industry when I was younger sparked my interest in it’ ygm?

I'm currently writing my personal statement for law. The most widely accepted advice is to start your ps by stating where your interest in the subject came from. And, however silly it sounds, I first considered law as a degree after watching Legally Blonde aged 12/13. It sparked my interest and from that I then went on to read books, articles and research etc about law. Obviously I'm not stupid enough to think that's what a law degree is going to be like but it is honestly what first put the idea in my head.

So. Should I use this to start my personal statement and use it as a way to show how my understanding of law has developed? Or would I be better to not mention it at all so admissions officers don't think I'm going to turn up and pretend to be Elle Woods? Many thanks!

Never, never (ever) start an academic personal statement with any reference to TV show or a film.

And for Law, it shouldn't appear anywhere. This is a highly academic subject leading to a serious professional career.
Just don't.

I think it's quite quirky/original to start it off this way, and can see it grabbing the reader's attention straight away. As long as it's used as just a starting point rather than the main focus of your PS, I would think it's ok to use it. Good luck!