I don't think this is the issue you want to get all fussy about, quite honestly. If dad has to go into work for a few hours during his uninterrupted (Doggie interpreted it accurately - uninterrupted means just that) parenting time, what's the harm in his girlfriend watching your little one? Unless she presents an immediate danger to your child, you shouldn't turn this into a fight.
Quite honestly, from the tone of your post it sounds as if you and dad have been co-parenting reasonably well. What if dad was leaving kiddo with his folks while at work? What happens when you eventually remarry and dad eventually remarries? How will you treat ROFR then? I'm not asking this in a snarky way, it's just a reality.
You have 15 more years of parenting together. During that time you can expect that both of you will, in all likelihood, meet other people, remarry, and have more kids. Work together, pick and choose your battles wisely, and treat dad's time with your little one the way you'd want dad to treat your time with her.
I've never cared for ROFR clauses because they can set up unnecessary arguments and future litigation if the parents get too nitpicky.

