I need some advice

DD3 is 15 months old (only 13m adjusted) and she is crazy. She is super destructive, and just plain mean. She hits and pinches. I've taken her hand and showed her to be "so soft! So nice and gentle!" but it's not working. I can't redirect her, she throws her self on the floor kicking and screaming and having a melt down. I've never experienced anything like this. My older girls are VERY sweet and relaxed and they have been most of their lives. DD1 is HF autistic, and she has NEVER had a melt down like this (infact in comparison to friends with kids on the spectrum, she's a positive angel...) I'm not sure what to do anymore. DH is all for setting her in her crib for a minute to calm down, but I just don't think she's old enough to understand a time out..

I started doing time out with my toddler when he was a year old. I put him in the playpen for 1 minute. I wouldn't recommend the crib because that is the place where she sleeps and is supposed to feel safe. Maybe use your bed for timeout though. That is what I do with my toddler now. He is nearly two but around 15 months I started letting him know his behavior was wrong and that he would go in time out if he didn't stop (example: If you keep playing under the sink you will go in time out). Well that worked for a while. Then I had to add in counting (If you keep playing under the sink you will go sit on mommy's bed in time-out..1...2...3... then I would put him on my bed for 1 minute)

He rarely ever misbehaves and when he does it is from him being hungry or tired. However all kids are different and you need to figure out what works best for yours. So far that is what works best with my toddler 

she is old enough for a time out, I've been putting my daughter for a time out scince she was at least that age....sometimes she will even put herself in timeout lol. but i wait till she is quiet then I start the timer for 1 min (because she is still only 1) when she turns 2 i will increase it to 2 minutes. I think the trick is though to wait until she's quiet. I wouldn't use the crib though cause then bedtime might be a fight? It's a pain in the butt but just keep putting her back in the same spot when she moves and re start the timer...she'll get the pic. But thats just what i do, there might be other methods that work better