Advice on dealing with young girls who want to hold my baby

[FantasticMrsFoxx]

I'm looking for some advice please on a situation that keeps cropping up with me and my 6 mo.
Several times recently when we've been out and about (in the park / meeting friends for coffee / changing her in public loos) I've been approached by girls of around 8 asking if they can hold her.
They always ask very nicely, but when I reply in the negative, I always get a "why?", or "I'll be careful" or “but I get to hold my young cousin".
I literally don't say "no" but I'm obviously quite new to this and I'm looking for a response that means 'end of conversation'.
Alternatively, do I have to accept that little girls are interested in babies, and just let them hold her?

I can't stand parents of children, after their child bugs me to hold my child, saying 'oh x loves holding babies' when they can clearly see I have said no.
I feel like saying, I'll tell you what, you go have another baby and let your child hold that one!!!