20 month old, pushing and hair pulling

[LemonadeAndSchnapps]

My DD (20 months) is an only child, and goes to my sisters house for childcare 3 days a week. My sister has three other children, a five year old, a 2.5 year old and a one year old. Her family will also visit ours one day a week, so overall my DD is around these children 4 days a week.

She has begun some really rough hair pulling, and will shove the youngest one over. She does seem to get jealous of adult time spent with the other children. She seems shocked when the other children cry/are upset, and doesnt really react when she is told off. We have been firmly telling her no, removing her from the room that the children are in, and she doesn't like that at all but this doesn't seem to be reducing the behaviour. She also will come back in very quickly but I don't think she is old enough to understand the idea of staying on a 'naughty step' as such, and seems upset enough at having been removed. At home we have cats which she also is always desperate to hug very roughly (not that we ever let her) but at my sisters they have a large dog which she just ignores completely.

Does anyone have any experience on how to go about discouraging this behaviour?

Instead of telling her off (which as you rightly say, she won't understand) why don't you model the behaviour you want to see from her? Stroking hair gently instead of pulling and hugging instead of pushing? Repetition is key. She learns nothing from being removed from the room, except that it makes her more unhappy and more likely to repeat undesirable behaviour... I have a 20 month old so not a stranger to some of these problems. For example he now pets our cats gently after many, many demonstrations (and very patient cats!). I've found Janet Lansbury and Sarah Ockwell-Smith's books to be really helpful for "mindful" toddler parenting!