Her AI story explains her copy costs. It doesn't touch your labor. Five hours at $350 is $70 an hour before gear and gas, and $200 puts you at $40 while she keeps the difference.
Separate the price from the format the price is quoted in. A per-listing number invites comparison against whatever the cheapest local media outfit puts on its website, and there is always one at $149. A monthly agreement sells a deliverable count instead: four vertical cuts and two long-form edits a month for $700, listings or no listings. The per-shoot figure stops being the thing she negotiates.
Before you restructure, get her actual listing count for the last twelve months out of her, not her estimate. If she closes 12 a year, $350 each is $4,200 and a $700 retainer is $8,400, and she won't sign it. If she runs 30, the retainer is cheaper for her and steadier for you. The whole plan rests on her volume holding, and agent volume is the least stable input you have.
Build a downgrade that isn't your price. A $150 tier, one vertical, phone shot, edited same day, no gimbal, no color pass, gives her somewhere to go that doesn't reset your rate for the other two.
Revisions are what will actually eat the retainer. Cap them at one round in writing with a named hourly after that, or your $700 turns into 14 hours in a month where she's fussy about music choices. And with three clients, one leaving takes a third of the book with it, so price like that's going to happen rather than hoping it doesn't.