I hear what you’re saying - and personally I think there is a lot of value in experiences like yours - both in terms of your relationship with your mum and also some of the social and life skills. However…
I think that from what we can gather on Instagram, Nina already had her nursery hours cut by Bex, there are little to no mention of play dates, groups or classes, so nursery is the only peer interaction Nina seems to get.
Bex has a number of days each week with her anyway, so pulling her out of the one regular activity where she appears to be with her friends seems unnecessary and unfair on Nina.