S.A.
3 weeks is a long time for a little one to be out of their routine and in the care of someone other than their parents... 3 weeks is a long time to be in the hospital! I am guessing that this time apart scared your daughter - especially if she visited you in the hospital... those can be scary events for a child and change who they are! NO telling what your daughter "overheard" about your illness or what she imagined - children have a way of making things their fault, so she may be thinking that you went away because of her! You are going through a lot but your daughter is also going through it and doesn't understand it and has lost her feeling of security (the talking back and being bossy may be her way of trying to get some control or stability back)... be patient with her and spend extra time focusing on her and her needs - not what she is saying but what she isn't saying and how she is feeling.
Healing blessings for you both.
stacy