To dream of your sister–in-law, denotes to features she has and those you find within your own personality. It is also very important the relationships you have with her in your waking life, as it could tell much more about a dream. If you have a great friendship with your sister–in-law, then you have good qualities within yourself and the ones you like in her.
Dream dictionary: i my sister-in-law dream meanings
It indicates that family structure will be changed.
…To dream of a birth signifies a death. One afternoon, at a garden-party, I met an old friend, who told me he had just dreamed his sister had had a child, and as he was curious to know whether that event had actually occurred, he was going to write at once. The dream was verified, but in a manner he did not anticipate; for, on arriving at his house he found a telegram awaiting him there to say his sister was dead! And again, at a cricket match one baking hot day in July I was speaking of dreams, when one of the players exclaimed with a shudder: I fear your interpretation of the birth dream is only too correct. A lady once told my wife that she dreamed she had given birth to a remarkably fine boy, whose eyes, however, were not both of the same colour. Two…