toddler and newborn

Hi all, can anyone give me any advice in dealing with a nearly 2 and a half year old and a newborn?! My oldest is so obsessed with our newborn and its really cute, she's like a little mother hen. However she can be a bit rough with her and I feel like I'm constantly telling her to be career to not touch the baby. I don't want her to start to resent baby or to think we love baby more than her. The other problem is that if she's in a naughty mood she's deliberately try and pick her up or grab her leg. Obviously I don't leave them alone together just in case but I'm struggling a bit with how to get the right balance between enough attention for both. We include my oldest when changing/feeding etc and ensure that we praise her when she's being good but I'm finding it hard...... Not sure if it's just hormones or where but I'm feeling stressed over it. Sorry for the long post but any advice would be appreciated!