Since we are only allowed to answer one question at a time, I had to edit your question so that there was only one. The nurse is complicit in Romeo and Juliet's elopement. Without the Capulets' permission and at Juliet's bidding, the nurse meets with Romeo to make arrangements for the wedding. She reports back to Juliet:
Then hie you hence to Friar Laurence' cell;
There stays a husband to make you a wife.
The nurse does not lie to the parents, but she is definitely acting behind their backs. After Romeo kills Tybalt, the nurse goes to find Romeo to bid him to come to Juliet's room, another act of loyalty to Juliet but of betrayal to her parents.
So, the answer to your question is yes the nurse believes that deceiving parents is sometimes right. She seems to value Juliet's happiness more than she does her loyalty to the parents. The nurse does not hesitate to arrange a wedding and wedding night between Juliet and the Capulets' most despised enemy: Romeo Montague.