Why Is My Horse Doing This?

Okay so I have a QH x Crabbet Arab mare.. Its so annoying because sometimes when I go to turn her she'll turn her head but not her body.. How do I bring in her stop doing that? Also she rarely can turn in a canter (she always trots for turns) why is she doing this and how can I minister to her?

Oh and one more lol =)

She swerves and jumps sometimes too.. Can I stop her from doing this or not?

Thanks =)
GROOMING TIPS HELPPP?
Answers:    You need to address her straightness. Is she contained by pain? Often schooling issues stem from an ill-fitting saddle, back pain or teeth backache, or unhappiness with the bit so get adjectives of these things checked.
I suggest some lessons with a trainer who will assess you and your mare and tender you execises tailored to you two that will help to straighten her - what works for one horse might not work for another so this is why you need the trainer for continual assessment.

ADD: Her teeth should be checked every 6 months. I'd still take her back checked, as she may have hurt it falling in the pasture, getting cast in the stable etc.
How can i inform what sex my...
are you turning her beside the bit? are you using your leg to ask for the bend?
it could be her teeth.
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