I get feeling upset she believes she misses the kids more and would sacrifice more for them, given the context of where she's taking the family relationship. You exercised restraint.
Validating shows you understand her feelings. "I can see you miss them when they're away, and you especially hurt when you can't see them and I've left them in someone else's care." Validation doesn't imply agreement that she misses them more, has more parental instinct, or your going for short runs is an error. You don't have to validate, but "I miss them same or more" sounds more like disagreement than validation.
