Here's an opinion opener I made up a few days ago that I've had some luck with over the weekend:

First, approach with your usual False Time Constraint and Root.

You: "Hey i'm in a hurry but I need some relationship advice really quick" (I like this line because they automatically assume its pertaining to YOUR relationship, so they lower their shields. Then you later mention its a friends relationship.)

You: "Imagine you get into a relationship with someone who at the time is in good shape. Then, after a few months of being in a relationship, they stop trying, and put on a significant amount of weight. Is this reasonable cause to break up with them?"

Her: "I think, blah blah blah"

You: "Okay, I'm trying to help my buddy through this, but he has no idea what to do."

Her: "Well he should talk to her about it"

(Here's a good place to add a 'projection' to the convo)

You: "Okay but thats not easy. Imagine for a second that You and I have been dating for a few months. You ask me if that dress makes your butt look big, and I said 'Yes', you would completely flip, right?"

Her: *Giggles* "Blah blah"....and you're in

This is great! I am totally gonna try this at some point.