in the first picture, you've broken the line of contact.
A riders hands and arms are noticible and can result in a poor placing if they are not positioned and used correctly. A seasoned rider will have a straight line from elbow, hand to horses mouth. This will insure a direct line of contact with the horse. Hands should rest in a natural position above and in front of the horse’s withers. Ideally the hands should be far enough apart that when the rider outstretches his/her thumbs they can touch each other.
Hands, ideally, should be with the knuckles 30 degrees inside the vertical. By keeping this in mind it will avoid flat harsh hands and/or stiff verticle fists.
You can see how your hands, the reins, and her mouth make a 'V' shape, rather than a straight line. In doing so, your horse has learned to evade the bit by sticking her head straight up (I have a half Saddlebred, so I know high head carriage!)
To teach her she can't evade the contact by sticking her head up, you have to follow her head as it goes up. Keep that straight line consistant as her head raises, like in the picture below. The horse in the picture's headset isn't low at all, but the rider has a more or less straight line from her hand to the reins to the mouth, keeping a consistent contact. The horse doesn't seem to be bracing against the bit at all, either.
Also remember, you ride a horse back to front. Even if you manage to yank her head down, you'll be forcing her into a false headset because you're not engaging her hind end at all. Use a lot of seat and legs and learn to be soft with your hands. I don't think the bit is the problem (as long as it's a mild bit), she's just found a way to avoid it.
Hope that helps!