To make the soup, add all soup ingredients to the slow cooker EXCEPT the greens and lime juice. Stir to mix, heat on low for 8 hours.
After 8 hours, remove chicken and shred with a fork, then return to the crock pot, along with the greens and lime juice. Stir and allow to cook for about 5 more minutes, until greens are wilted but still bright green.
Prepare southwest salad according to instructions, top with diced avocados.
Serve soup in bowls topped with avocados, shredded cheese, tortilla strips, lime wedges and if desired cilantro.