You cannot "forbid" her to go on these. Yes, that would be controlling.
All you can do is state what YOU are uncomfortable with. What she then does with that, is up to her, but it's also very telling.
If you want to take it "all the way," you can make it a "boundary," and say "You can do what you want, you are a grown woman, but I personally cannot live in a marriage where my wife goes on trips like these." But I don't think you want to make a marital stand on this issue, absent some hard evidence that she's doing anything adulterous on these trips.
