1. Someone just swam a mile and a half through Class 4-5 water, and has been out of contact with people for a prolonged period of time. There is, in my opinion, an immediate urgency to make contact if it can be done safely. You need to check for signs of hypothermia, shock, flush drowning, etc. While the decision to swim across by the guide was likely because she was a customer...the reason the local rescuers didn't was because they are trained to never enter the water unless its a last resort.
2. You've got a 13 year old girl from Texas...the odds she knows the signs of hypothermia or any of those other conditions are fairly low, and relying on her words from across the river could be missing critical signs. You're also several minutes from helping her on one shore, as opposed to
3. As others have mentioned, having someone qualified and competent handling ropes, a raft, etc on the shore with her is a huge advantage to any rescue scenario that is put in place. Relying on someone young and likely scared to be responsible for their safety is silly when you can have a trained professional assisting her instead...that's the entire premise of guiding.
4. This extends beyond this scenario to general rescue...but a lackadaisical approach to the 2nd half of that rescue could be what turns a safe scenario bad. What if the river is still rising...is her location still so safe? What if she is hypothermic, or swallowed a lot of water? What if she sustained a head injury in the swim and doesn't remember it? There is ALWAYS an urgency to turn a bad situation back to normal as fast as you reasonably can...and its only heightened when cold water, long swims, and inexperienced people are involved.
A lack of urgency, because the girl was on the shore and seemed safe, led to the prolonged 2nd part of the rescue. 90 minutes is beyond ridiculous as a time period to pendulum the girl back to the other shore...if the guide had his choice, he'd have likely walked her back upstream, had her pendelumed across with a rope (and could have easily clipped himself in and held onto her during that maneuver), and had the girl to the medical personnel in probably 10-15 minutes. A 10 second swing across the water to cut the rescue time by over an hour is reasonable to me