I've seen two questions about followers and armor and the conclusion was:
- They will refuse different kind of armor than the one they're trained for (eg. heavy vs light armor)
- They will not equip weaker armor in favor of stronger armor
I've given Ebony Armor (78 armor; Heavy Armor type) to Lydia, enchanted with health regeneration and flat HP bonus. She still refuses to wear it. I've stolen her Steel Armor (56 armor; Heavy Armor type), but not only that she didn't equip the Ebony Armor - she also has respawned the Steel armor again.
Is there any way to get her to wear the Ebony Armor save cheats?