Her tail is beautiful, so I would just give it quick snip straight across the bottom at about fetlock length.
As for the mane, I would cut it. I really don't like long manes with the exception of a few breeds, so I would definitely cut that one.
Mane can go loose for XC, and jumpers. Hunters, if it's a recognized rated show or bigger, then do hunter braids. Other wise, I leave manes loose as well if it's just a small hunter show.
Dressage, either little plaits, or the button braids. I always plait the tail as well.
"You're just as sane as I am."~Luna Lovegood.