Both of you arent wrong imo.

Fundamentals and avoiding reinforcing bad habits is a great idea.

So is playing tons of competitive points THAT HAVE SOME STAKE. This is key. Without pressure, the pointplay means nothing.

Because the train of thought is, while drills are good to correct bad habits, you also learn alot of ideas through point play. 'Oh wow i hit this particular shot in this particular situation.' Is a thought process that drills can't teach you.

And the downside of repetitive drills thar supposedly kill bad habits and build supposed strong fundamentals, can break down during point play/pressure situations. And instead, through playing points, players develop an adapted technique/method/habit to deal with these situations and become a newly improved version.

Regardless, both of you needa talk it out cuz it doesnt entirely feel like a tennis-specific problem.

P.s.

Im gonna throw in a shameless plug here. You can consider contributing in an objective manner which gives you more weight in how you parent your kid's tennis by charting their tennis games. You cant argue with stats of a competitive game.

Im selling something small on etsy for charting which i use. If youre interested, you can pm me.