I wonder if your MIL is having some memory issues? Strange to behave like that. My mum is embarrassingly over friendly and playful with children wherever she sees them- supermarkets , anywhere. She was diagnosed with Alzheimer’s afternwenhad noticed this strange over familiar behaviour and playfulness with children. Exactly as you describe but with strangers children. I know this sounds a terrible thing to say but worth considering that she’s feeling uncomfortable in social situation because she herself has a problem? Be kind ( you sound like you will be) She may not realise. It’s how I noticed mums problems.
She suddenly seemed to not understand not to do things like that and still continued after being told by me. What I’m saying is it may not be alcohol, there may be a problem? ( I’m also a MIL and a granny) of course she may just be being stubborn because she won’t be told what to do. That ones in us all sometimes!
Estranged Son and Future Granddaughter
To think that London, or anywhere else for that matter, does not belong to any one demographic