16 month old being violent

[Miniope]

Not sure if my title is the right one but basically on the last 2 weeks, my 16 month old has suddenly become really violent. She is constantly hitting, pulling hair, scratching, occasionally biting. My 3 year old seems to be getting the worst of it but she's been doing it to everybody. She does it if someone tells her 'no', if they have something she wants and don't give her it, sometimes there doesn't seem to be any clear reason, particularly with my 3 year old. At the same time as all this she is a really happy and bubbly wee toddler. She loves my DS3 but can go very quickly to hugging and kissing her to scratching and pulling her hair. This starting has coincided with a week away with my 2 step children (8 and 12) who were doing lots of hitting and play fighting. I did ask them not to do it around the wee ones but it took asking quite a few times for them to eventually stop. I don't know if she is now doing this because she's seen that or if it's just developmental as some things I've read online have said it can be.
She has hit all her milestones and I've had absolutely zero concerns about her until now. I'm not exactly sure how best to deal with it though due to her age. Does anyone have any experience with this or advice?

Behaviour is communication
What is she trying to communicate?

Sometimes it's frustration but other times there's no obvious or clear reason.

What are the triggers for her doing this? You say she can go from hugging & kissing your 3yo to scratching etc very quickly. Is the 3yo being too exuberant in her response to the hugging & kissing or is it going on too long and the 3yo just wants out?
What happens when she does this? How do you react? Even if something seems minor to you, try and see if through the eyes of a baby. Is it a way of getting attention? Is it a way of getting some 1:1 time without the baby in the way?

Usually it's her hugging my 3 year old and she's most likely to start when my 3 year old starts to move away. I've been telling her no but because she's now doing it so much I felt like it wasn't having an impact and there's no point in just constantly telling her no so I've started trying to redirect her instead. She can just be sitting beside someone though and start hitting them out of nowhere.
She also pulls my 3 year old's hair a lot. My 3 year old has very very curly hair and I'm not sure if this has anything to do with it as she doesn't tend to pull anyone else's hair.

If there is no clear reason then I doubt it's "violence" and more likely a set of schemas she's developing ie going through the big leap that occurs anywhere 16-20 months. https://www.onehundredtoys.com/understanding-schema-play-in-toddlers/ some basic info here

Thank you. That was very interesting to read. It makes sense, particularly for the times when the reason why isn't obvious. Do you have any suggestions as to the best way to respond?

Have you tried all walking away and ignoring her when she does it. Also giving lots of attention when she’s communicating non violently.

I can do that myself but she rarely hits me (maybe that's why). Thinking about it now, she tends to do it to others when they are very close to her so maybe she is wanting space from them? My oldest stepson has been really giving her a lot of attention but his way of doing that tends to be picking her up or putting his face right in hers which she often doesn't want and will hit or scratch him. Although tonight she walked up to my mum to hit her out of nowhere.
Ive been trying to give her lots of attention to for positive behaviour.

My 9 month old is currently doing this, i thankfully don’t have any small children to worry about (my youngest next to her is 9 years old), when she does it she is watching for a reaction? Cause an effect is very entertaining, “if i pull said persons hair they say oww/scream/cry” probably why she mostly does it to your 3yo as they probably have the best reaction to it.