Have you upgraded Eliza to get her Character Ability to retain Sekhmet? She has an upgrade she needs to get first before you can allow Sekhmet to stay in battle
Unless you're pressing the Sekhmet button that sends her away
just for clarification as well, this is the upgrade Sol is talking about
i wouldn’t really think of it as “unfair” because all characters require an upgrade for certain skills to work properly for them. besides, it’s the first upgrade you can get in the character part of the skill tree and doesn’t cost that much, even for golds.