Liiza didn't like to see Khan hurting himself for her sake. She didn't want him to put so much effort into getting accepted by Zalpa and the Niqols society as a whole. She would gladly take his place and shoulder that burden, but opposing his resolve would only go against what made him so exceptional.
Khan's selfless determination was unstoppable when it came to a few topics. Liiza would only risk offending him if she tried to oppose that resolve, and she would even fail to make him give up on the matter. The best path was to show him her support and take care of him properly once he succeeded in his plan. In Liiza's mind, Khan couldn't fail when he put his whole self into something.
Zalpa didn't expect that turn of events. Liiza and Khan were extreme characters, but she believed that they could suppress each other's radical features when they were together. Still, they actually ended up condoning and supporting them if the situation required it.