She's not you. The time YOU text your friends has nothing to do with your wife's friendships. Saying he shouldn't text things to friends of the opposite gender is saying that people of the opposite gender can never be truly friends. You obviously have a view on gender and friendships that your wife does not necessarily share.

You can't "say" anything to become comfortable. Saying something means you are telling your wife to change her friendship to cater to your insecurity. If you trust her, trust her to text a friend at weird hours. If you don't trust her, then your relationship isn't viable. Trust is a choice that you have to willingly make.