This is pathetic behaviour, she must have serious insecurity issues going on there, needing to be top dog all the time. Just ignore it, be yourself and next time she feels the need to outdo you, say very gently “ it must be exhausting being you” ..... or go the other way and endorse what she is saying ie. “Yes, I’m sure you will be the absolute best” .... maybe that would make her look at how absolutely absurd she is. As you are sadly estranged from your other family, are you able to chat with your son in confidence just to voice your concerns ? So sad that what should be such a wonderful time, is spoilt by such a ridiculous woman. Babies need love and support from all the family, it’s not a competition.
To think that London, or anywhere else for that matter, does not belong to any one demographic