The writers of "Facts of Life" were obviously beefing up the 9th and final season with opportunities to showcase Lisa Whelchel as Blair, as the plan was to carry her over to a spin-off series.
In this, the 18th episode of season 9, Blair crashes her car after falling asleep at the wheel. She wakes up in the hospital with a massive gash across her forehead. The episode essentially focuses around her horror at no longer being "perfect"; moreover, that her only worth is her looks and those will forever be tainted.
There's a long childhood story about a spotless white dress that Blair tells, setting up a metaphor for her now blemished face, but it comes off overwrought and trite. Jo is the only one who finds out about the injury, and chooses to tell Blair's boyfriend after Blair breaks up with him in a preemptive attempt at stopping him from calling it off with her over her tainted appearance.
The episode wraps up with Blair and her beau patching things up and everyone reassuring Blair there is more to her than just her looks. The whole thing is an obvious attempt to showcase Lisa Whelchel's acting chops, but unfortunately she just doesn't have them. This may be the reason why the spin-off was axed: Whelchel simply isn't as good an actor as Charlotte Rae, and there's no way she could have pulled off an entire series as the motherly headmaster.
Additionally the writers really didn't think through the scar situation, as the following six episodes feature not a trace of the injury in question. There are references in conversation in this episode to plastic surgery, but an injury this severe would take numerous surgeries over a year if not more, so a real continuity situation arises.
It's not the worst episode in a series that featured more "very special" ones than you could count, but the trite writing and shaky acting make it one worth skipping.