I'm concerned about a friend who's a doting wife but isn't allowed to have her own life
What makes you feel that this friend is not allowed to have her own life?
She's 24 years old now and she's still to be tied up into that relationship.
It's understandable that you are concerned about your friend. However, it's important to be sure that the narrative that you are sharing it truly how she feels. Talk with your friend to gain a deeper understanding of what she wants for her life.
I know she's unhappy with her life, I just can't prove it.
It's important to consider that there are numerous reasons that a person may be unhappy with their life, including fianancial, educational, and social reasons. You should find out for sure what is going on with your friend.