I think Barbara's suggestions are great, especially if this behavior has just recently cropped up, but may I offer another perspective.

There's a 7 year age difference between my kids, too. And I also thought, oh, it'll be great, because with that difference, they will never fight. HAHAHAHAHAHAHAHA! Wrong!

For a while, I was astounded -- what could they find to fight over? Well, I'll tell ya: "Don't touch my stuff!!" "Don't copy me!!" "Shhhh! Stop talking to me!" They just annoy each other on occasion -- okay, the occasions are daily. The younger one gets upset because the older one ignores her. The older one gets upset because the younger one gets into his things and sometimes does do the annoying copying.

Face it, yes three-year-olds are cute, but they're a lot more cute to their parents than to others -- including siblings. And ten-year-olds can be polite and compassionate, but not so much when their space is being invaded and they are always the one who has to understand the limitations of their little sister -- it can seem like a one-way-street for the older sibling, for sure.

The one thing I can tell you is that, at least in my case, it does get easier. As your little one gets older, she'll start to understand some of the rules and she'll require a little less of your attention as well. That will be easier on your older daughter. And I think when your youngest is a little older, there will be more games that she can play with her sister, and more activities they can do together.

The only other suggestion I have is to have some special activity that you share alone with your oldest. For example, I take mine out to breakfast maybe once a month, just the two of us -- it's a special thing that is his alone -- a privilege of age, if you will. If you can add in some activities that your oldest gets to do with you because she's the oldest -- manicures, perhaps, or maybe a Zumba class -- she may see that each age has its own perks.

I've heard of spending one-on-one time with the older one - the "privilege of age" - as commenter SandyEE puts it and heard that it works well.

As an observer of families, though, I think if the younger one is also the "baby of the family", that is, you don't expect to have more children, you may actually be letting the little one get away with more than she should... because she's the baby of the family.

I have a eleven y.o. girl and five y.o. girl. My oldest is always complaining because my little one has fewer jobs around the house, the discipline is different and so on. When it comes to her perception of fairness, she can be emotional, irrational and sometimes downright explosive. I have addressed this by offering to treat her and her sister EXACTLY the same. That means no sleepovers, no school socials, more supervision, earlier bed time, fewer choices, no earning cash for being the neighbors' mother's helper, no allowance, no week with her aunt in the summer, no trips to the mall to choose own clothes, etc.... The list is quite extensive because she is a good kid and I have been able to give her quite a few freedoms. When faced with losing those freedoms, she generally drops the arguments and silliness, at least for awhile.