Leadership Scenario Survey

Imagine yourself in the following situation and consider what the best approach may be to this commonly-cited problem for Mountaineers leaders: 

New member "Maria" has signed up for your _____ trip (hike, backpack, scramble, climb, paddle, sail, etc.). You've listed it as a "moderate" trip but noted that you intend to be back to your cars by 5PM so you can make it to a dinner with your boss (that came up after you had posted this trip and already had a few people signed up. You didn't want to cancel on those people and figured you could make it work). It's a 12 mile trip with some modest elevation (or current), but you've seen many new members handle it just fine in your 12 years as a Mountaineer leader. 

You listed the trip as "Leader Permission Only" because you can't afford to be late to this dinner. You get an email notifying you that Maria signed up and you go to her profile to take a look at her experience. She just joined last fall and has only been on 3 successful trips so far and you don't know the leaders of those trips. You also notice that she's got 3 "cancelled" trips in her profile. When you call her, she doesn't answer and you leave a voicemail. She doesn't return your call until 2 days before the trip and explains that she had a big deadline at her job. She apologizes and begins asking what you think about the trip this weekend: will the weather be good?, how many times have you led this specific trip?, how many years have you been a Mountaineers leader?, etc. She seems eager to go on the trip so you agree to put her on the roster. 

During the trip, Maria shows up 10 minutes late, but appears to be well-prepared except for the fact that she put her gaiters on the wrong legs (or cannot seem to zip up her dry-suit by herself). No concerns are brought up in your pre-trip briefing and the first half of the day goes well. After lunch, however, Maria reports that her back is hurting too much to keep up with your pace. She says she's had problems with it before, but not for the last few months. Long story short, you end up having to cancel the dinner with your boss because you don't make it back to your cars until 7PM. You ask your committee chair not to let her sign up for any more "moderate" or "strenuous" trips until she completes some successful trips with good references from other leaders.