MC could have just unsummoned the mage when he got lip/violence from her.
Would ruin reputation and relationship though, and eventually devolve to a situation of using the summons while the summons hate him and help just so they don't die. Though, maybe they'd eventually prefer suicide to being in that situation. Hard to judge the proper amount of selfishness in that situation. I might ask what the motivation is of the summon to not work hard, and if they can keep up - and what reasons there should not be expedient gain of power.
If the summons have agency, part of the problem with this writing is that there is an unspoken presumption that video game characters have one dimensional personalities and scripted / limited potentials for "growth". This, along with gacha addiction of course, interferes with the dynamics of a MC treating the summons as actual people. Actual people, you cannot just summon/desummon.
The mage character is doing what it can to humanize itself to prevent being desummoned and suffering. That is respectable, but the MC is the issue here. As usual.