Actually, yes, it was wrong of her to do such a thing. If she had been a less jealous person then things might have turned about better globally. And Hagar acted pretty awful as well. She had been selected by basically a queen to play what was a very important role in that society and upon seeing that she had been blessed with a child by the king of the tribe, she mocked her queen and allowed her own son to mock the heir. Kinda stupid to do that.