Nurse’s strengths are that she loves Juliet and would do anything for her, but her weaknesses are that she can be selfish and talks too much.
Nurse’s daughter Susan was Juliet’s age, but died young. As a result, Nurse considers Juliet like a daughter. She has raised Juliet from a baby, and loves her. It is because she loves her so much that she is willing to be the go-between for her and Romeo, and even willing to help them be secretly married. Nurse feels that Juliet would be better off with Paris, but she decides to do what Juliet wants.
For all of Nurse’s strengths, she certainly has weaknesses. Like Friar Lawrence she is too short-sighted, not really seeing the damage caused by their hasty marriage. In addition, she talks too much. People who need to get information out of her sometimes find it difficult. Romeo teases her about this.
I can tell you; but young Romeo will be older when
you have found him than he was when you sought him. I
am the youngest of that name, for fault of a worse. (Act 2, Scene 4)
Of course, whatever her strengths and weaknesses, Nurse is not entirely to blame for what happens to Romeo and Juliet. She and Friar Lawrence both are just trying to help the young lovers out, and break the feud.