Have fun at the BBQ! Consider taking another step back from controlling the experience--at the beginning, let her introduce you to whomever she wants to, politely excuse yourself to use the restroom or get some food, then focus on others. See her again whenever you see her again whether that turns out to be "sooner" or "later".
This is plan A.
There is an art to breaking away. Do not do it too soon. Do not wait too long. You definitely want to do it before she does. A good time is when it is just you her and one other person. As long as you are actively in the covo, stay. Once the convo goes to just the two of them talking back and forth without you, excuse yourself to the restroom.
This is a problem for me. I think she may say it as soon as we arrive. She has complained in the past that I do not socialise enough and hang around with her at parties. I might just say it after we get a drink when we arrive. I find it very hard to do small talk. I am reading a book on it this week in preparation.
