I would be very disappointed if she didn't have a career or qualification first
I only say this from my own personal experience. I thought I wanted to be a stay at home mum, so wasn't motivated to get any type of back up plan as I thought I didn't need one.
Turns out financially that wasn't possible and I also didn't feel productive with in myself .
I am now in the process of studying multiple courses and secured a full time job trying to build a career so in a few years time if I have another baby I can CHOOSE to be a stay at home mum because I can return to the workforce once I feel ready with already having previous experience.
I wouldn't want her to have the regrets I had by not doing that the first time round as it is more difficult now already having a child to juggle it.
The financial independence and super is also another reason.
I would just like to add - my parents have always worked full time so I've never experienced having a stay at home parent, but when ever I have needed them they have always been there, if my parents needed to leave at a moments notice to help me, they could and did. They worked themselves into a position where I could still come first. So I don't think it's fair to say only stay at home parents are able to do that.