She's not about to force anyone to sit and this guy certainly seemed squirrley enough that she doesn't want to make him feel obligated to do anything he didn't want. It was perfectly acceptable if someone wanted to just lurk on the edges and observe.

Still, she wants to make everyone feel as welcome as she can, and that means at least one tiny interaction. She doesn't approach him immediately, waiting for a natural lull in her own conversation that's picked up by someone else and easy to extract herself from. She approaches him and crosses her arms loosely, keeping a certain distance out of respect.

"You might be surprised. I don't think it's a bad idea at all to set up barter and trade of skills. I could probably use a few self-defense lessons myself; I'm not sure how useful knowledge of taking out a mugger is going to be here, but knowing how to fight a bear? Might be worth trading a few knitting lessons for."