Australian Shepherd help please?

My aussie is 8 years old and is very healthy. The only thing is she is constantly frustrated and is really starting to get annoying. We have three other dogs and she seems to get jealous whenever we pet them, we even give her the same amount of attention if not more to keep her calm. Since she is older she isn't as hyper anymore but she is barking and pawing at people constantly. She goes out, two minutes later comes back in, a minute later wants back out, then she comes in and starts barking at us.. She is not usually like this, we walk her 3-4 times a day and she is outside for 2-4 hours. What should I do?