It's absolute nonsense, she should just be honest and say 'I'm bored already, we fancied a change' if they move.
Re the house she's said it's not suitable for kids but never why. Never seen a balcony or heard one being mentioned and anyway she could get a gate for that, there are roads wherever you live and the inside could be redecorated in a more child friendly way. It has enough bedrooms, bathrooms, a large kitchen a garden, parking near the house (to get baby in and out easily). There are families of multiple children living in substandard accommodation next to busy roads, etc. they may not have a car so have to bus/walk everywhere. Some will never have the prospect of buying anything.