I would go w/ a bosal w/ mecate.. unless you are trying to teach the mare to neck rein. If she is a well trained normally going western type mare, she should know that.
AND I would go with a side pull OR a bitless like thers
Side pull http://www.codywesterntack.com/shop/...od&productId=9
Bitless type http://www.joshnichol.com/sidepulls.htm
One looks more english than the other one...
the reason people use mecate is its prickly on the horses neck and helps teach a young horse to neck rein.
If you go with a Wintec, get one with Cairs panels/ interchangeable gullet system.
That way if you change horses, or with riding your horse looses weight.. you can change the system so it fits the horse better..
Congrats, be safe, wear a helmet!! and have fun.
Always end the session or ride on a good note.. if you are going well, but are a little tired. Stop and give the horse a pat and call it a day. That way you have confidence, aren't getting too tired or sore (LOL), and you and the horse are enjoying it.

Carol