You need to do two things, Leigh. One, find the right boot. Two, stabilize that bad ankle past what a boot聴any boot聴can do.
Asolo Echo BootsAs for the boot, you聮re looking for a light hiker that offers reasonable support and good traction. Lots of choices there. Asolo聮s Echo boots ($100; www.asolo.com) are just the ticket: light, reasonably breathable, with good traction. An over-the-ankle design also offers more support than low-cut hikers. For a little beefier boot that聮s still very comfortable for day-hiking, try on the Montrail Solitude II ($140; www.montrail.com). These have the advantage of one-piece leather uppers, a more durable, more weather-resistant design than boots that are pieced together from several bits of material. And, the Solitudes are fitted on a women聮s last, meaning they聮ll fit better than some boots that are sized for women but not really designed for women.
I really don聮t think you need waterproof boots (the Solitudes already are very water-resistant), but if that seems appealing to you, Zamberlan聮s Micron GT Hiking Boots ($150.00; www.zamberlan.com) have a Gore-Tex liner to keep just about any water out聴unless you step in over the boot tops!
None of these boots, however, will hold your ankle in place if you really start to roll over on it. So buy a good-quality brace, such as the Swede-O Inner Lok 8 ($45; www.swedeo.com). It聮s a lace-up brace made of non-stretching material, so once it聮s on and secure, it聮s almost impossible for the ankle to rotate sideways. And it will fit under most footwear (not all聴buy a brace, then shop for boots). Several models resemble this one, so don聮t hesitate to try a different brand. But it must be a lace-up brace made from Cordura or similar tough material; a stretchy, elastic brace won聮t cut it.