It may be more on her than on you. I can have trouble orgasming during sex, but it is largely because I don’t relax correctly in the moment. Too many thoughts about performing in my head combined with muscles that are too tensed.
Therapy has helped a lot more than any technique. If she wants to work on this for herself, maybe she should try it. If this is just your insecurity showing, you should probably drop it and help her finish off with toys.
Have you considered a sex therapist? Sometimes they are better at hearing clues as to what the problem is since they have experience talking to a lot of couples.
It doesn’t have to be the kind you get naked in front of either, just an intimacy therapist that you can both safely describe your experiences to.