I also don'r get why some people are making a big deal out of Laura sleeping over with Nathan.
It just seemed like a realistic scenario to me. She had a long day at work, and fell asleep after a good fuck. No malice there, that's just normal.
Nathan said "I'm sorry bro, you must have been looking forward to spending some time with her, I'll tell her she needs to make it up to you tomorrow."
The first thing Laura says the next morning is "yesterday was so exhausting, I slept for 14 hours, I'm sorry I couldn't make it back home last night, I swear I'll make it up to you today."
You guys are really making mountains out of molehills. She didn't sleep over to cuck the MC even harder, or because she cared more about Nathan, or anything like that. She was just tired after a hard day, and fell asleep. No boundaries were crossed.