Dream about significant other marrying someone else is a portent for your own state of thinking wisely and the struggles to make a decision. You are trying to escape from your problems. You are not able to express yourself in how you really feel about a situation. The dream signals some wasted effort or loss. There is no such thing as a free ride.
Significant other marrying someone else dream is an evidence for thoughts from the primal aspects and less developed parts of your subconscious. Areas of your life are out of control. You need to stop what you are doing and rethink about the situation before moving forward. This is a harbinger for your inability to overcome current difficulties. Something is weighing on your mind that you are confused about.
If you dreamt about significant other marrying someone else:
If someone tries to get you involved in any kind of argument today, be sure to steer clear, especially if it is your partner (current or prospective) or close personal friend. The slightest provocation could start a real row, and this would not do either of you any good. In a day or two you will not even remember what the problem was all about anyway.