Looking at the rules (which are imperfectly written), the reclusive roll only needs to be made Before the witch is hired -- once she's agreed to work for your warband she sticks around for as long as you pay her.
I think your judgement on the skills is good -- gain a spell from her list or choose from the Academic skills. There's no indication in the article, & I don't think the unofficial hired swords have any errata to fix these issues, so as long as your opponents agree to those rules it should be fine.