I guess everyone's idea of relationship, or being a "couple", is different. "married", like the expression "married at the hip" means joined/connected, so what one person might mean by "let her go", could mean "be ok with her going" as in "I don't mind"... Like "would make me upset", if you said "That might make me upset" as a response to "What would you think if", what is the difference between that and flat out saying not to do something? Both signal the same thing, is there a choice? Always.... Two different roads going to the same location, one isn't wrong over the other and they're both the same distance.
"She does for herself, not for me." Sure, but if while doing for herself, the consequences get passed along to you, it's not just herself anymore? Hence, "Let her go" as you're part of the equation as well when it comes to potentially dealing with the consequences of the action. That's why a "partner" consults with the other. Maybe it is asking for permission, but there's reason, two people in the car that feel the direct consequence of the decision made to hang a left at the intersection without stopping. Hanging the left, without consideration of whether your partner wishes to or not, could be considered a little narcissistic by some.