In S1 E3, we all know that Sarah Lynn shows back up into Bojack’s life after a public mental breakdown. During the drive to the hospital after she stabbed herself, Todd expresses concern and says “She is losing a LOT of blood Bojack!” Bojack just replies with “beautiful day though, right?” This may not have been intentional, but I think that was already foreshadowing him waiting 17 minutes to call 911 during her OD in S3. He’s definitely not driving her as fast as he could be with that sentiment.
theres plenty of foreshadowing. this, saying that she’ll die tragically young, her not having a reason bojacks funeral will be the next one cause she’s high, and her saying the only drug she needs is horse. i’m sure there’s more Im missing but this is off the top of my head