Warlock – “Expansion” [4th campaign, 2nd mission]

You can and you should. You'll be wandering and fighting through three more missions together with her.
By the way, she was the only one of mine who could learn "Fireball", "Meteor Shower" and other useful spells. So in some battles it was more rational to use her.

Thanks for the advice. I'll give her the troops and send Railag to the Castle to learn spells. I think I'll try to give her the "Scholar" ability so she can pass her knowledge to Railag. Though, I didn't understand why Railag couldn't learn these spells? Didn't you level up his chaos magic? IMHO - one of the most useful skills for a Warlock. My Railag already knows "Fireball".