Baby is 6 months old

By 6 months, she can already do quite a lot. Just be careful not to encourage sitting too much right now. She really doesn’t need to sit up at 6 months yet. And it’s normal that she wants to make crawling movements but can’t yet, because crawling usually happens about 2 months later. You could encourage and help her with rolling over, though, since that’s what she needs to do first before sitting up and crawling.

Yeah, that's right, sunshine. I also find it really strange that she can sit but doesn't roll over. She did that twice two months ago and then stopped. She hates lying on her tummy anyway. I don't encourage sitting, but you see her constantly pulling herself up and trying to sit, and if I don't help her, she starts screaming and gets very angry. So then I help her up, and she's happy again. I try to encourage turning with toys and constantly turning and demonstrating, but she doesn't want any of it.

Every baby has their own pace.
I wouldn't worry too much. Some babies are really into rolling over and tummy time, while others aren't.
Mine (5.5 months) also wants to sit. I sometimes help her sit, but not too often because it's not great for her back.
Our little one also hated tummy time, but it turned out she had a tight muscle in her neck that was causing her pain. Once an osteopath loosened that muscle, she started rolling over. That was when she was just 4 months old. And now she rolls in every direction when she's on her tummy (360-degree turns).

But don't fixate too much on the 'average' of what a baby can or can't do. There are babies at 6 months who still don't do anything at all.

What else you can do to encourage her is to sit on one side of your baby and let her use the hand furthest from you to grab your finger. Once she has a good grip on your finger, you can gently pull her toward you.