My wife was always behind me ..until she decided to start ...weightlifting a year and a half ago.
Yes... not running, not any cardio training (she does it too and she always did), but the simple weightlifting.
She is 5'2" and it was always difficult for her to keep with big and strong man.

Her average speed increased dramatically - 15-16 mph when she was 30.. Today she is 41 and it is no problem for her to keep 19 mph for more than an hour..
It is more than enough for me.

Of course I'm trying to stay in the front and she is sitting on my wheel.
Of course she has comparable bike and decent wheels, nice shoes etc...

But she was riding the same level of equipment and 10 years ago and it did not work unitl...like I said.
Also, she is not only faster on teh road, she became much better on the trail....