I am not an instructor. I do have some thoughts on how you can help your friend out though. Look up CJ Wiley's older stuff on his youtube channel. He talks about stance and "aiming from the center of your body" in those videos. He even uses a sword to demonstrate what he means. If you want to go down the rabbit hole of what our bodies are actually capable of here's an experiment:
Imagine some point on your body that is centralized, this is an anchor point. I use my belly button. Someone could use their chest, groin, big toe or whatever but I find the belly button to be one you can easily incorporate and it's centralized. While up and aiming, vividly feel/imagine where this anchor point is in relation to the shot line and the shot/aim you are taking. Using your body awareness, keep this anchor point in mind as you get down on the shot. Pretend it's a glass of water and you don't want to spill a drop. This breeds consistency and consistency is king in this game. I like the belly button because it's related to where your core muscles are and you can keep a good posture with it.
There can be several anchor points in pool. Your center body, your bridge hand, your shooting hand, where you're looking as you get down, footwork and probably many more.
Tangentially related, when banking I like to find the most accepting part of the pocket for a given bank and touch the slate at that point. I "load" this info into my bodily/spacial awareness and then address the bank as usual. It looks silly, but just this simple act improves my percentages.
There's all sorts of ways to align with shots and many anchor points/trigger points in pool. You have to have curiosity but there's a lot to be discovered in this game. Pay attention to things.
If you want to go further down this rabbit hole, check out several videos on traditional Japanese archery. There's a lot to learn there. In every sport, players have a "calibration ritual" and they can be quite personal. Most, if not all sports have this. Pool is no different. The difference is, in say little league baseball, you're more likely to be taught how to do this, but many pool players never even think about this. Many call it PSR, but often PSR instructions only include the mechanical stuff and you should also be including "feel" or calibration. Watch a cat wiggle it's butt before pouncing. It's calibrating, and we should be on every shot. Make sure the world is level and true before shooting. This applies to upright as well as low stances. Build a personalized calibration "ritual" into your game. Practice it until it becomes a rote habit and you can go far. The key is be consistent and do it on every shot. This game rewards the dedicated and punishes us when we get lazy.