My wife will ride with me on short rides, but on double centuries she likes to start about an hour before I do, then I pass her about lunch time +/- 100 mi. and I finish the double about an hour before she does.
She likes it that way, since she can ride at her own speed without slowing me down, plus she tends to ride a bit above her comfort zone when she's with me, since she always "thinks" she's slowing me down.
So I say, talk it over, and whatever works for you two is good!
Rick / OCRR