Meals are not a done thing here and I desperately wish they were. I would absolutely go with meals! Supper is an app in my area that does fresh meals as an alternative to takeaway. Or just make something and take it by.
A bottle of champagne to toast the new arrival would be nice.
Spa days are awesome but see if they have an expiration date. I didn't have a babysitter with my first until she started at nursery at a year old and it would have been impossible to use before having a sitter. Hopefully she has a better support network!
Supper looks fab, but isn't in her area (Dorking), boo. The Dorking thing would also make it difficult to take something round. Though I imagine that if I were to take the Thameslink down there while cradling an 8L crock pot, I'd have a cracking pub story in the end.
Anyway, it's good to know that food would be appreciated (don't give a toss if it's not a done thing, that only makes it more useful). Leaning towards Cook --
https://www.cookfood.net/ -- because they offer vouchers, online ordering and delivery. That way, she can get whatever she wants, stock the freezer, buy some more later, have lots of flexibility. She's not (as she tells it) either a very good nor very committed cook and, without getting into unnecessary detail, I don't think there's necessarily going to be a strong nearby support network. So this seems like the most helpful way to go?
I agree about spa things: It's a nice gesture, but even if you get one without an expiration date, there's still got the stress of planning and coordinating everything, and that can become a burden that detracts from the experience.
Champagne is also a good shout! Or maybe gin, knowing her ...