I plan to travel from A to C via B, buying a Network card discounted A-C ticket. A friend is meeting me at B so can I buy her a discounted B-C ticket on my card provided we travel together or will I have to purchase an A-C ticket for her too ?
Thanks.
I think it's fine - I've done the same a few times - though as she has to be accompanying you, you should break your journey at point B - i.e. she's not supposed to be on the platform at station B with a Railcard-discounted ticket waiting to join you (and your Railcard) on a train that stops there.
(Though I and three friends have illicitly done the latter - the ticket office at station B was closed when it should have been open, and the TVM didn't offer GroupSave, so the three of them bought Network Railcard discounted tickets and joined me on the train - I had started at A, on a train that called at B, and we all got off at C.)