It would be better for both to be on the same account going forward as, even without the Broadband, there would be discounts you're entitled to such as Multi-Line Discount.
Unfortunately it's not quite as simple as 'adding her contract' to your account.
As she is due an upgrade, if she were to be transferred using the "Change of Ownership" process (to move it from her name onto your account), you would be unable to upgrade or change her plan for 6 months due to the bedding-in period after the transfer - which is not ideal.
Instead what could be done is she could be moved to Pay As You Go and then moved back onto a new contract under your account once this has been actioned, allowing her to take advantage of the same EE One offers that you can get.
I would advise speaking to EE Customer Services on 150, or going into a store, to explore your options on this front as this can be quite a complex process with multiple steps and some support needed.
Over all, once it's all done it'll be much better financially in the long term.
