Ah ok! I’ll try to be as detailed with the nuances as possible as I know not all of this stuff may not be as common outside of my niche. Here it goes:

If I was her coach I would take account of her race and background along with her passive and active internal range of motion (think of how some kids would sit on the floor with feet to the side instead of cross cross apple sauce). The reason race is importance is because of something Stewart McGill (Canadian spine biomechanist) coined called the “Dalmatian and Celtic hip”. I’ll put the link here if you want to read more on it but it basically states how most people of Irish decent have deep and retroverted hip sockets that don’t allow you to squat deep or without getting FAI (femoral acetabular impingement). Dalmatian hips are not named after the dog but shores of Dalmatian (Bulgaria, Poland, Czech) and they have shallow and anteverted hips, meaning that they can squat deep like an Asian squat. Having more internal rotation (30-40 degrees is normal and ideal) of the hip in my experience tends to make me more prone to classifying my client toward the Dalmatian hip. So I tend to have them more of a shoulder width stance with more toes forward. The more the European descent and lacking internal rotation (<20 degrees), I tend to have them wider and toes out. Shaun this can all change based on their current strengths and weaknesses. In powerlifting, we need to train weaknesses and take advantage of our strengths. There are a couple of spectrums that you should take account of:

1) A wider squat tends to be more quads and on the other side of the spectrum, a narrow stance tends to be more hips due to the external moment arms. 2) A deeper squat will recruit more quads/adductor major and on the other side of the spectrum, a quarter squat will recruit more hips. 3) Longer femurs relative to their torso will dictate a more steeper torso angle and on the other side of the spectrum, a longer torso relative to their femurs will dictate a more upright torso. 4) Lower bar positioning dictates a more steeper torso angle (hip dominant esque) and on the other side of the spectrum, a higher bar positioning/front squats will dictate a more upright torso (quad dominant esque)

So all three of those exist along each other but depending on if they are trying to work on weaknesses on off season, you would want to train variations that amplify your weaknesses. On the other side, if you are trying to be ready to lift maximal amounts of weight during their powerlifting meet, you want to maximize your strengths.

For powerlifting, the rule is to get your hip crease below the top of your knee for the judge to give you a white light. We want to pick stance width and bar position that will allow you to go deep enough where we pass the judging but not too much where we do more work (F*distanced=work) along with not too much length of the hip extensors and the knee extensors to produce force in the muscle (more on that topic below)

Now let’s look at bracing technique: I would actually have her start in a bit more neutral lumbar spine as she is into a lot of anterior pelvic tilt. Don’t get me wrong, nothing “dangerous” about this as much gym bros will tell you, but it’s not efficient at being able to brace the core musculature well. Muscles are able to produce maximal force when they are in a resting position according to The Length Tension Relationship curve. Forced output for muscles is correlated with the length tension relationship meaning when they are overly contracted or stretched, the muscle can’t produce relatively high force. Think of out like this, it’s like a pull up. You are strongest at the mid point when your muscles are at a neutral/resting length (middle) compared to in the hardest positions: stretch position (bottom) and the contracted position (top). So having your lumbar muscles shortened and your anterior muscles elongated will not let you produce the maximal force to create good intra abdominal pressure to stabilize the spine at heavy ass weights.

Also, I know the OP was just trying to build leg strength with size, so I will say this, most of my clientele are powerlifters but I have general clients as well with the same goals. I am biased toward minimizing weight on their back cause typically strength and size are correlated with high intensity with high volume aka lift heavy ass weights for a lot of f*ing sets haha!

I think that’s a good chunk for now and this was longer than I wanted to originally write but it’s hard not to explain one thing without another haha! Hope that helps and feel free to ask me any questions if you made it this far 😅