Pay me to quit requests from poor performers

We are a not-for-profit. One of our poor performing managers with just over one year of service met with their boss yesterday and said that they are no longer feeling engaged and they want to quit but can’t for financial reasons. They said they can’t be without a salary while job hunting. They asked if we can pay them out for their resignation. Apparently the employee is quite toxic and we want to enable the exit ASAP. We were thinking of telling then that we have considered their predicament and that if they send us their voluntary letter of resignation this week, we will arrange for her to have a 4-week taxable lump sum “retirement allowance” paid to her. Is there anything I should be mindful of before I proceed?