I don't know if this is the solution but its how I managed to tell her about it. I injected Adrian's PC when the relationship with anna was "2-3 hearts" level. After I reached "5 hearts" level it gave me the option to tell her about the discover (talked to her in the kitchen).
p.s. I don't know if its relevant but before speaking with Anna asbout Adrian I managed to kick Josef out of the house