Such a tough one. It sounds like there are multiple behaviours that need addressing. I would seek out professional advice. It is nice to get other parents advice – but every child and parenting experience differs. My child has ADHD.
Personally I found that never giving in to a child’s demands when you’ve said no because otherwise they will learn if they carry on enough, you will eventually give them what they want.
No matter how much kicking, hitting and screaming etc they do, not caving will eventually help you in the long run. It will reinforce that this behaviour will NOT be rewarded. If your child hits you, try to be proactive and in a calm voice say something along the lines of “I don’t like when you hit me” and walk away to a different location. You may find your child follow you and *hit* again, but repeat the process. The aim here is be consistent in whatever route you take, as repitition is they key for any behaviour changes throughout life.
Remember to also take time to praise your child when they have done something good.

Oh and when your child has ADHD and suspected Aspergers, than I think you should get a referral for a psychologist.
I would be careful with smacking her bum, even though you do it very gently. Cause when you want to teach your child not to hit kick and bite, you should even more so give the good example by your response at her yourself.

Personally I believe in positive and negative reinforcement of certain behaviours. The best way to reduce negative behaviour is by first finding out why she behaves that way and be proactive not reactive (with other words prevent it) as you can see behaviour as a form of communication. Very important to praise every positive behaviour and give it attention and when possible ignore negative behaviour.
When you feel it grows above your head I would try and get a referral for a psychologist.

I see this was posted in 2014, I wonder how you are going now? Perhaps her therapist (assuming she has one due to her medical conditions) might help. As parents it is hard to not react to the behaviour and work out why they are doing something which may be an unmet need or not being able to communicate clearly

time in, or time out. explain why

Are you seeing someone about her ADHD and suspected aspergers? Ask them to recommend how to manage and hep her behaviour, my son has ADHD and it was very tough going (he’s now 18). He still defies me even now, I was too lenient on him but did what I could at the time to survive. Specialists did help

I think you’re doing everything right. Being a parent is one if the hardest jobs

I think you are doing everything perfectly. You just have to be consistent.

You have to be incredibly firm, strong, and consistent. Your little one must learn boundaries, even children with much more profound problems than your daughter learn boundaries. It is not easy and you and your daughter will need all the love and support of your family and Friends . You may even need to enlist the guidance of some sort of child behavioral specialist to give you a starting point. Most of all you must keep letting your daughter feel your love.

Oh getting down to her level is perfect. I have a “thinking chair” I put in the laundry so it isn’t near the TV. And I ask my daughter to sit on the chair and think about what she is done and to come out to say sorry etc….. my daughter is only 2 and I only have to say, “hold on, you are close to going on the thinking chair” and her behavior settles down. Hopefully this might help, but I know it can be tough. I too get told I am too soft but sometimes they can just be too cute!

Sounds like you are being a great mum.
She does need some discipline but just be consistent and don’t give in once you start see it through,
but also pick your battles, think is this really worth a tantrum over?