1) I agree that Tempest is a pretty mediocre PrC, that's not really worth the heavy entry requirement. Scout 8 also doesn't seem to make much sense.

2) I am a huge fan of Flame Blade, though there's a huge ongoing debate as to whether or not you can apply Power Attack to it. If you rule that it does, then a PrC that progresses her Druid casting a few more levels and a Wand of Flame Blade would certainly be worth it.

3) If she's not going to be a strait Ranger, she should trade in her spellcasting and animal companion. There are a variety of variants (Unearthed Arcana, Complete Warrior, PHBII, Complete Champion, etc).

4) Assuming she does pick up Ranger 6, then the feat combo for her is Karmic Strike and Double Hit (Miniatures Handbook). Karmic Strike gives her an AoO whenever someone hits her. Double Hit allows her to attack with both weapons when she makes an AoO. Though precision damage only applies once, its a great way to have a massive damage output. Best when combined with Claws of the Vampire or something similar.