L._.
She has you figured out. You feel sorry for her or you can't stand the crying. Maybe it's a mix of both or maybe you feel guilty for letting her cry. But it's time to change some things.
When you are cooking, she goes in a high chair nearbye with toys. If she throws the toys on the floor, she sits with nothing. If she cries, she cries. Get a good pair of headphones and some books on tape. It will help you to ignore, ignore, ignore. At night, you check her pants and leave the room. I don't believe in leaving kids in wet pants. But she's old enough to not need either a bottle or food or for you to sit next to her.
As far as the hitting the other kids and then rubbing them and saying nice, she's just trying to figure it out. Do what you feel comfortable with. It's not wrong to tap her back or time her out, or just keep doing what you are doing. Whatever you do, just keep it up and be consistant. If she keeps doing it, put her in a play pen with toys and tell her it's because she's not playing nice. It's not a time out. It's just giving your other kids a break.