little girls just don't know

Yesterday morning, as I was getting 2 kiddos out the door with my 5 bags (yes, I look like a bag lady as I leave with my breast pump, lunch, A's lunch, A's nap bag, and K's bag), K reached up and grabbed onto A's hair.  I say grabbed but really, he launched and twisted.  It looked painful.  She obviously cried.  As I unglued A's locks from K's hand, my crying 3 year old told K. "no, you don't do that."  then she turned to me expecting me to punish him. "Isn't he going to time out, Mommy?  We don't hurt our family."  I tried to explain that he is just a baby and he doesn't understand.  She seemed to accept this so they went to their respective daycare centers and I on to work.  

I'm not sure if she was processing my statement all day, conniving for later, or just very quick witted.  But, A. did not have a night of making wise choices.  As we were all playing peek a boo with K. after dinner, A. said "look Mommy" and then promptly swatted at her brother looking at me for my reaction.  She hit him so lightly that he didn't even notice.  But, not wanting her to find this acceptable, I put her up in her room.  I'm sure you are able to guess what happened next. ..  "Mommy, sometimes little girls just don't know."  At first, I didn't make the connection so I just said, "You, A., know that we don't hurt our family. We don't hit other people."  She sat in her room for 3 minutes and then we were on our way to the bath.  She promptly dumped half of the container of her favorite bath toy, courtesy of Aunt Beth, little colored tablets that change the bath water color.  Luckily, I caught the container so we had black water but at least still have options for future baths.  A's response, "Sometimes little girls just don't know.  We need Mommy's to help us."  A light bulb went off.... Now what do I do?  
a. Some things little girls do need help with, but you know better than to hit and throw your favorite toys
b. acknowledge that K. gets away with things because he is little but she knows better because she is the big sister
c. ignore and carry on with her testing her limits of being a "little girl"
d. decide to put K. in fake "time out" next time so that it is fair in my 3 year old girl's eyes

So far, A and B have worked.  We'll see if I result to D. as the day goes on.