It would not occur to me to stop a partner going in this particular situation, unless they were doing this constantly to the point of unfairness. Is it a marriage or a prison? She clearly thought you would be ok with it. Now you have done the heavy handed thing and she is (rightly) rebelling.
Make the most of it to ensure you can have a day out on your own or better still, play the decent partner, encourage her to go to her event and arrange a special day out for the 2 of you later in the week/month thats romantic and fun. Also, have some special time with the kids and do a bit of extra bonding with them. Its fun to have a parent just to yourself.
Who would you value the most – the supportive romantic or the sulky ‘do what I tell you’ person?