Riliane is indeed,difficult to deal with on an evil playthrough. Party members will stop following orders if they don't like you, and most evil acts give negative reputation with her, you can try to boost your relationship by doing some 'good' actions, or try to win her over with "red bouquets" which can sometimes be found/looted be bought from certain shops. As long as you can bring your reputation with her up high enough she will listen again. Alternatively an option to just not have to deal with her is to either choose to kill her at the start, giving you a life steal attack, or sacrifice her to the slime queen, which imbues all summoned slimes with a basic healing spell.