Her Lady of Steel And Fire

Nadezhda, princess of the isolated Grand Duchy of Moesia, has been betrothed to a foreign prince in a diplomatic maneuver. Needing to travel without attracting attention through hostile nations, her father hires a single female wandering knight to serve as her guard.

As the pair travel towards the unwanted marriage she finds herself instead drawn towards the her guardian in shining armour. Only to discover there is more to the other woman than meets the eye.

Or, perhaps the issue is that there is very little that does not meet the eye in regards to the fully armoured woman.