"Place the violin to suit the length of arm. Too far to the left and the player has trouble reaching the tip. Too far to the centre and the bow is quite crooked."
Here Fintan places Emily's violin to suit the length of her bow arm.
You can try this on your own. Stand with your back to a wall, with your shoulder-blades touching the wall. Place your violin, then put the bow on the string from the air at the heel, the middle and the tip.
When working on a 'straight enough' bow at the tip we need to develop the 'in & out' bowing action, which Emily demonstrates here.
The Violin & Your Body - Introduction
Violin Bow Technique - Bow-change Action on Bow
Violin Bow Technique - Exaggerated Finger Flex