True Seeing is a Divination spell that states
For the Duration, the creature has Truesight
While Mind Blank states
one willing creature you touch is immune to […] Divination Spells
Let’s say that the Rogue was cast Invisibility and Mind Blank, and the Wizard cast True Seeing on himself. The discussion at my table hinges on the fact that True Seeing doesn’t target or affect the Mind Blanked rogue, so his immunity is not relevant. The Wizard would simply gain Truesight and would spot him.
How do these spells interact?