Yes, anterolisthesis is another name for spondylolisthesis. So her L5 vertebra (the bottomost of the lumbar part) is sliding forward on the S1 vertebra (the top of the sacrum part). It can be genetic aswell (when you're missing a tiny bit of bone in the joints at the back of the spine) so may not be due to disc degeneration or an accident. There's different grades of slippage (1-5, I think). If it's small (grade 1), and not causing much pain (back pain and/or leg pain), they often don't operate. (Although it may be different when its genetic...maybe they like to treat it early to prevent later damage?).
Hope that helps a little for when she sees the surgeon.