Having the same issue. Been mostly following the guide, and as far as I can tell I've done all the scenes with Betty prior to the 1.9a section. I've gone back and redone some of the scenes with Betty, because no matter what I do I can't trigged the "Catch her near Michelle's bedroom in the evening and reveal yourself" part. Not sure I missed that's causing it to not trigger.
Not sure if it will help but try peeking on Michelle and NOT going back later. I'm pretty sure that you need to do an early evening visit to the room and NOT go back later BEFORE you can catch Betty the NEXT night. I had issues as well but remember seeing something about needing to only visit at the first time.
So, try to visit in the evening, then wait until the NEXT evening and visit again. Like I said I'm not sure, but think that's what is needed.
Hope that helps.
Just tried it, and unfortunately it doesn't help. I peeked on Michelle for a week straight without visiting her room later that night, and nothing took place. I then spent the next week alternating between peeking on Michelle and then leaving, and peeking on Michelle and then coming back that night. Still unable to find Betty or catch her, etc.
