I'm struggling to see why my friend has started to avoid me

I met another mum through my daughter's nursery and we were good friends for a while. We looked after each other's kids now and again, and we'd have nights at home, setting the world to rights over a couple of glasses of wine.

- Dear Coleen

I remember thinking how great it was that I'd met someone I clicked with and that our kids were friends, too. However, over the past few weeks, she’s been blanking me and going out of her way to avoid me at drop-offs and pick-ups. It’s become really awkward and I've absolutely no idea what I could have done or said to make her behave like this. I'm genuinely mystified.

What do I do? Should I confront her to find out or should I just leave it and accept the friendship is over?