Oops! Trudie and I gave different interpretations! If you do find out from the doctor, can you set us straight? Thanks! As you can tell, we are NOT doctors, but we try our best to help people while they are waiting for solid answers.
It sounds like a single fluid filled cyst. Odds are in favor of it being benign and it's small enough to leave alone and just watch (in most cases). Age makes a difference in what action they'd prefer to take as well as medical history. Are you still waiting for a doctor's opinion on this? Regardless of what we think, the doctor's opinion is the important one. I hope you get all good news!
It likely means she has a complex cyst. Over 95% are benign and there is lots of good information about types of cysts and symptoms on the health pages (top right). What is her doctor's plan? Please keep us posted.