If you're close enough with her I'd say, "Hey, I didn't see you at that mandatory safety meeting thing last week. Did you come in late?" See what she says.
When the time comes for the next one, I'd ask her if she wants to walk there together. She might not want to go and be forced to sit next to someone she doesn't know in a room full of strangers.
Past that, I don't think I'd say much else.
Regardless of how close you are, I wouldn't report her absence unless it impacts YOUR job safety. If her missing these meetings is going to put you in danger, I'd probobly bring it up to my immediate superior, see if he can send a reminder memo or call a department meeting to remind everyone (thus not singleing your coworker out).