Yes, I agree with her coming more than once per week too. It's pretty tough to build up routine with one day. I had a 2.5 yr old until my recent move. Her mum is pregnant and I noticed a change in the girl's behaviour once she figured out what was going on....some of which you noted. Of course, you must be stern when it's warranted. I found having 'special moments' just with her also helped...very imtimate and very focused. I'm sure your girl is feeling quite displaced and just not sure where she fits into everything, but she's bent of making her presence known by any means necessary. When she's behaving appropriately, just slather on the love...maybe comment that she must be a wonderful big sister. Lots of hugs, cuddles and praise for being such a wonderful, special person. She's no longer queen of the castle and I'm sure she feels it. It certainly helped with my little one.