I'd look at Southampton, KCL and Manchester... but they are all highly competitive. You will also want to consider transport links as your daughter will need to consider getting to placements from wherever she is living as well as getting to campus.
Southampton offers dual field nursing (so children's nursing + adult or mental health) as well as children's nursing on its own. Dual field is 4 years.
If she's intending to work for the NHS then the ranking of the uni isn't as important as it is for some other careers.