There’s a significant event happening at Cal’s aquatics complex Friday. Yes, the No. 1 Cal women’s swim team hosts No. 12 USC. Former Olympian Amy Van Dyken will return to work for the first time since she suffered a life-threatening accident and spinal cord injury that has left her paralyzed from the waist down. “It’s a big deal,” Van Dyken said by phone, before her grueling daily physical therapy session. On June 6, the six-time gold medalist was driving an ATV (and not wearing a helmet) near her second home in Arizona when she went over a seven-foot drop. A few days later she went through a spinal fusion surgery that was so risky that her surgeon advised her to say goodbye to her husband. [...] she has kept her spirits up and relied on the mental strength she gained as an elite athlete. Van Dyken remains optimistic that through new developments, she may some day walk again.