Wanda and Jillian have an odd, complex relationship. They possibly were friends before Faq fell. Wanda believes their two Fates are linked. Jillian remained concerned for Wanda even after breaking free of Wanda's spell.
It is implied in Book 2 – Text Updates 010 that before the fall of FAQ Jillian and Wanda were romantically involved. They appear to still 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. This relationship is implied to have existed in Faq during a flashback.
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 has repeatedly attempted to persuade Wanda to leave Stanley's side, once while being held captive at Gobwin Knob, again during a fly-by visit to Gobwin Knob before the Coalition attack, and yet again when they parleyed at Jetstone. Her attempts to influence Wanda was 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 Summon Perfect Warlord Spell 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 during the Battle for Gobwin Knob from having secrets that Jillian didn't know, Jillian has secrets unknown to Wanda. Wanda probably did not know that Jillian had rebuilt Faq and become a Queen, until she decrypted Ossomer. She still doesn't know that Jillian's Royal Heir will pop fairly soon, or that Jillian has formed separate alliances with the Royal Crown Coalition, the Western Giants, and Charlie.