It seems that I'm the only one who thinks she's trying to make conversation and just not doing a very good job. If someone said they were worried about going to Oklahoma b/c of tornadoes, I probably would say something breezy about how odds are they'd be fine and I wouldn't let it ruin my trip were I going there. I'd probably also make a comment if a good friend complained about losing their luggage - that's what you do to acknowledge something a friend says. If you don't want commentary (good or bad), you don't put it out there.
OP, I really feel like you're letting your past color your impression of her a bit much. I truly don't read any of it as condescending or even advice-giving. It's just statements. You've even gone so far as to say she's trying to lord her intelligence over you even though you're the one with the advanced degree - that just sounds like a major self-esteem issue on your part (I'm sorry, I realize I'm being awfully blunt). Granted you have every right to unfriend or block or what-have-you if it annoys you. I think the suggestion above that you just delete comments you don't care for and tell her you've already discussed why if she asks is a good one. I also suggest take some time to look into why she's making you feel this way and learning to separate her from people in your past who hurt you. She isn't them and I very much doubt she's trying to be like that.
There's a big difference between saying, "I'm sure you'll be fine, try not to worry, enjoy your trip" and saying, "You're just being silly."
Of course most people who are being obnoxious are not doing it on purpose, just like most people with horrible B.O.aren't doing it on purpose.
That doesn't make it any more pleasant to be around. It also doesn't mean you owe them an audience, or that you have low self-esteem for saying, "enough!"
Indeed, knowing when you've had enough is a sign of proper self esteem.