This, for me, can be a good or a bad situation. Depending on how we feel first thing in the morning Suzanne and I can differ in pace by a solid two-to-three minutes per mile. She's willing to walk with me on the days when I feel badly. I've sacrificed my "workout" on the rare occasion she's awakened feeling sore and beat. We cannot, however, run together. Any time we have tried to do this in the past the end result has never been positive.
There's no way you can force a person who runs a ten-minute-per-mile pace to run two minutes faster. Neither love, money, nor small arms can be used by any coach to repeal the (seemingly) immutable laws of physics...and of human physiology.
So it's then a choice between the lesser of two evils: Leave her behind on a run, or run at her (slower) pace. A runner can damage themselves not only by running much too fast, but also by running a pace that is much too slow. An individual runner's performance capabilities - maximal and minimal - are defined by physiological limitations. The biomechanical limits which affect stride length and turnover are much like the systems of a motor vehicle. Vehicles which have been designed for operation at higher levels of performance can be operated at a lower level of performance, just not for an extended period of time. Like a sports car or a muscle car is designed to be operated at a particular level, a runner who runs at a much slower pace than their stride mechanics are built for will either expend too much energy (bad!) through excess contraction and expansion of the large muscle groups or damage their "drive train" and/or "suspension" (worse) from excess strain on the smaller muscle groups of the lower extremities.
It doesn't take too many instances of running much too slow to damage a runner. I tried to run "with" Suzanne two years ago when we were in Hawai'i. Three 45-minute morning jogs at ten-minute mile pace led to a Thursday afternoon appointment with a massage therapist. Yes, I had fun chatting as we watched the early morning surfers and joggers in Ala Moana Park. Not at the cost of 50 bucks which could have been spent on other cool stuff.
I've also encouraged less-speedy runners to come run on Sunday mornings by instituting what I call "'Blackhawk Down ' Rules." We leave nobody straggling behind. A runner can go off the front if they feel sprightly, but heaven help you if someone is left to their own devices on the road. This attitude comes from being left to run solo from a porta-john two miles from the end a long run some years ago. It wasn't so much the two miles at race pace which upset me as much as what happened the following week; the same group let the teenage son of one of the members dangle blocks off the back of the pack.
Before the run starts, we talk about how long we need/want to go, in time or distance terms. If time, I use an out-and-back course, or a loop which is close to the length we would get on an out-and back. If a loop, the faster runners are charged to walk back toward the slower ones at the completion of the time period, unless they're at the end. If out-and-back, naturally, the group turns around at the half-time. In a perfect world everyone gets back to the start at nearly the same time. On a bigger loop, however, I've asked the faster group to turn back at mile splits or time splits to regroup with the slower runners. This way the faster runners definitely get more mileage and see the slower runners more often.
This morning, for example, I went out with one of my marathoners on the same 7.5-mile loop on which Suzanne and another one of my friends were training. By the time Jim and I hit the point where Suzanne had two miles left in the loop I joked we were running "ten the hard way." We finished the loop, then I walked back to meet up with the slower pairing...who were only two or three blocks from the parking lot where we started.
There are inconveniences to doubling back on a run to regroup with slower runners, but I feel it provides the opportunity for faster runners to see and encourage their group peers. And isn't encouragement part of the reason for which we run with others?