well for me bro i really did not allow it...asking for my permission is just like telling me straight in the face that she likes to go out with someone else other than me...she did oblige and i was happy for her respecting my decision.
it's really your call, if you and your GF are in a open relationship well that should be okay...if you are both committed to each other then it's a no-no...especially if it will be a romantic date...
BTW, wa man nimo gi sulti kung unsa nga date- friendly date, group date or romantic date...in my case it was a friendly date.