I have an almost 4 year old, Grace and a 15 month old, Caroline. Grace doesn't do well with her sister. She kind of tolerates her. She's very rough, pushing, taking toys out of her sister's hands, kicking if Caroline gets too close. I don't get it, she does play will with other kids. We do timeouts, taking toys away, we tried to really lay it on thick when she does something nice for Caroline - nothing works. She's always been like this. Even when Caroline was an infant, Grace wasn't interested in her.
I don't know what else to do, I don't get it, I feel like a failure. What can I do to get her to be nicer to her sister?
Re: I'm at my wits end
I really like the book Siblings without Rivalry.
I'm sure you're probably already trying these things but I'm just suggesting whatever works with my girls. Make sure Grace is getting enough positive attention from you and DH. Taking her out without her sister is always a good idea too. Be careful not to blame things on the baby (ie don't say "we can't go to the park because Caroline needs a nap"). Spend some time talking about feelings and "using your words" and what to do if someone isn't "listening to our words" (go talk to an adult).
You probably need to really supervise their interactions right now and try to intervene before Grace starts to get aggressive. Redirect the baby and help Grace express herself without getting rough.
I hear jealousy from your post. I think that your older one is probably somewhat jealous of her little sister. I would try to give her some undivided attention (a special outing with just her), and maybe some responsibilities to show she's a "big kid." Maybe by feeling more important, she will learn to treat her sister with kindness.
You could also try a sticker chart and reward her for good behaviour.
But, I will tell you that my sister and I (4 years apart in age) fought constantly, and nothing did any good for us. Hopefully, your girls will be better than what we were. My mom didn't do anything to intervene though. I think she was sick of it.