Ive gotten it in ysoldas tiny house sleeping in a single bed, the only one in there, so long as she was in the house when i woke up. Got it everytime I slept at hjerim with my wife in the house. Ok just tested on my new guy thats married to Borgakh the steel heart. Kept her living at "her house" which is her dads longhouse in the or stronghold of Mor Khazgur. Like three other people live there in the house besides her and its all single beds except her dads (the chief). I wait until night and she goes inside, find her sitting at a table then go sleep in a bed for eight hours. Wake up with lovers comfort. Then I told her move to proudspire manor, then I fast travel there and wait 24 hours after I go in. I dont even see where she is and go sleep in my bed 8 hours and awake woth lovers comfort.
I need to check this then. When married to Ysolda I had her move into my Whiterun house, so she is always there. I know that sometimes you don't get the message but the perk is active (you have to check your stats to see it). I'll try just sleeping with her 'in the house' and see if the perk is active when I wake up.