Ding! I believe Lydia is ready to go at level 8.

Summary of changes:
- Ability score increase: +1 WIS
- BAB increase to +6/+1
- Saves increase to +6/+2/+6
- Additional 3rd and 4th level spell slots
- Additional 7hp
- Divine Strategist feature: Tactical Expertise
- War (Tactics) Subdomain feature: Weapon Master
- +3 skill ranks (+2 background skills)

Weapon Master will be fun - I've wanted to use it in a campaign ever since I first saw it!

And, I've been forgetting to mention because it's kind of a pain in play-by-post, but the Divine Strategist's Master Tactician ability means that all of Lydia's allies should be getting +2 to initiative as long as they can see/hear her.