Wanda and Jillian have an odd, complex relationship. They possibly were friends before Faq fell. Jillian remained concerned for Wanda even after breaking free of Wanda's spell.
They appear to have had a romantic and very intimate relationship during the times when Jillian was captured by Gobwin Knob, but it's unclear how much of that is genuine, how much was the spell of control Wanda cast on Jillian, and whether there might be other factors involved.
When Jillian breaks free from Wanda's Suggestion Spell, Wanda absorbs the full damage from the spell's abrupt termination. It's possible that she absorbed this damage deliberately, in order to avoid harming Jillian. She asked Parson not to croak Jillian, immediately after the spell broke.
Jillian tried to persuade Wanda to leave Stanley's side, but her attempts to influence Wanda in Book 1 were hindered by the fact that she didn't know certain critical facts about Wanda. Jillian did not know about Wanda's role in the First Battle of Faq or the prediction that Wanda would someday gain an Arkentool. Wanda did mention the spell that summoned Parson in passing after she interrogated Jillian at Gobwin Knob, but Jillian still doesn't know many critical facts about Wanda's relationship with Parson.
While Wanda benefited in Book 1 from having secrets that Jillian didn't know, Book 2 begins with Jillian having secrets unknown to Wanda. Wanda probably does not yet know that Jillian has rebuilt Faq and become a Queen, been ordered by Don King to pop a Royal Heir, or formed separate alliances with both the Royal Crown Coalition and Charlie.