Daughter jeopardising relationship

It isn't really the daughter that is jeopardizing the relationship. Kids do what kids do and that includes being smart mouthed, disrespectful and limit pushing. That you see this as being the daughters fault seems to indicate inappropriate blaming and some anger towards the child.. Realistically what is jeopardizing the relationship is the apparent differences in what you think is acceptable and what the child's parent thinks is acceptable. Partnership relationships weather the storms of problem children every day. If your relationship isn't handling it well...you may want to look at what that says about the relationship rather than blaming the child. As the non-parent you have to leave this situation to the parent. Any attempts to discipline will probably be meet with resentment from the child and anger from your s/o. This isn't to say that you have no options. You do. You can go through your s/o to request the changes you want to see. You can also state what your limits of tolerance are. Ultimately you can also decide if this relationship is right for you.