You could promise her a ride on the train to Portsmouth, as there is a nice purpose built shopping outlet at gunwarf quay (old HMS VERNON for you history buffs). Then you could pop along to the Submarine museum.
Or similar vein, southampton, she may go to ikea and you could go to the Solent aviation museum. Supermarine etc. Jeffrey Quill collection.
Or Bieulieu motor car museum, and then Bucklers Hard for lunch at the pub, and a visit to the museum there. Bucklers hard is where Nelson's favourite ship the HMS AGAMEMNON was built.
Sorry to say, but i would think twice about the Bournemouth aviation museum, it will take five minutes.