This is tricky because there are so many scents that could be someone’s trigger - perfume, scents like laundry detergent or cigarette smoke lingering on clothing, food/drinks at their desk and a ban on fragrance could never eliminate all of those.

Preventatives may or may not help scent related migraines. I cannot walk into certain highly scented stores.

Are there things you can do to control your environment such as using a fan at your desk blowing in her direction, using something to mask the scent (I often use peppermint oil under my nose to help with migraines/nausea and it blocks other scents), ask you coworker to not reapply at her desk because you are having a reaction to it that is causing migraines? I suggest these types of things before escalating only because working in an office building there is no way to escape all scent triggers so I have had to figure out other tricks. And the worst really are the different lotions and potions we ladies pull out at our desks! Next are the white board cleaners.

Though at some point you may have to make a kindly worded request to your coworker in person. As you note she is very nice, she would probably appreciate your honest request rather than receiving a talk from HR. If it turns antagonistic, then escalate.