I find that most people are fairly understanding as long as it doesn't effect them. Coworkers and friends tend to give the benefit of the doubt and are understanding. Sometimes you have to remind them, but usually that clears things up quickly. Sometimes, those of us with chronic migraine also develop some anxiety about missing things or letting people down, even if people are very understanding.

The gaslighting... most of the time it's people who don't know enough about migraine (or don't care) and start to see patterns as laziness, avoidance, or similar. Miss a few wednesdays in a row? Guess what, your manager might think you're avoiding that wednesday team meeting... Miss a few tests or a presentation in class? Well, clearly that's because you weren't ready and wanted to buy yourself more time... Sometimes they've bought into some misinformation that all you have to do is eat some magical salt every day and you'll be cured. Or they disbelieve the existence of chronic conditions entirely. That's where a manager will find a way to use some performance metric to get rid of you or a professor will treat you like a drain on their time.

All of this is in the context of the United States (I'm sure many other countries handle this a lot better, as usual). It's really uncommon for migraine to be well-understood at work or school. Especially if you don't have a current diagnosis, which is also common since doctors tends to brush it off or require some extreme logging to even consider, or insurance companies will refuse to pay for the testing and MRI scans usually required to have an official diagnosis and meet ADA requirements. Like any non-physical disability or illness, schools and employers tend to continually forget and fall way short of ADA recommendations. Especially with chronic conditions that may have phases of being worse or non-existent for months at a time. "Well, you didn't have this problem last quarter, so what gives?"