My L6 daughter was diagnosed with both spondylolisthesis (vertebral slippage) and spondylolysis (stress fracture) in November. The treatment was 4 weeks full rest with only light conditioning (exercise bike, chin ups, stretching. NO running or jumping or swinging on bars), then started very light PT after 4 weeks (massage and stretches) that's rapidly increased to a massive list of 20 exercises she has to do every day, so what Nutter Butter says about "lots of PT" is no joke . It was 8 weeks before my DD was allowed to run and jump again. She is currently 11 weeks post diagnosis and has been cleared to vault (it's L6 so just timers, no hard surfaces for her yet), swing bars and add tumbling. She still is not allowed to dismount onto a hard surface from bars or beam, nor to do bar skills up to vertical because of the risk of overbalancing and arching; nor can she do front or back walkovers or handsprings. Her coaches have alternative skills planned for her to meet routine requirements and those are what she's working on for L6 states in a month. Happy to talk about those if it gets to that point for your DD.
My DD's spondy showed up pretty clearly on the xrays; in fact, to answer Nutter Butter's question as to why the chiro might suspect spondylolisthesis, my DD's orthopedist could actually palpate her spine and feel an indentation where the slippage of her vertebra occurred over her sacrum. It's possible that Amel's chiro can feel the same thing with her DD. Amel, you will find a lot of information on this board, but there's something I learned that never popped up on any of my CB searches on the topic that I wanted to put down here for future searchers. You will need to have at least 4 xrays (maybe MRI's too like Nutter Butter says) done if she has spondylolisthesis: a front xray, a lateral xray and a flexion xray and extension xray (one is where she's arching and then another when she is bent over, I can never remember which is which!

) The first two will determine the grade of the slippage (amount that it's slipped). The latter two are critical for determining the instability of the slippage if she does in fact have spondylolisthesis. So if she DOES get the spondylolisthesis diagnosis, it is very important to know if the doctor considers the slippage
stable vs. unstable as well as
the grade of slippage, so be sure not to leave your doctor's office without that information!!! If it's a grade 1 (least severe) but stable slippage, she can still be cleared to do gymnastics again. This is what my daughter has, and it's apparently not uncommon for gymnasts with this grade and stability to progress to the highest levels of the sport with diligent self-care and knowledgeable coaching. If it's an unstable slippage, that's when you will run into potentially career-ending problems. So spondylolisthesis and spondylolysis are very serious conditions, but not necessarily career-ending, esp for lower level gymnasts. I did not know to ask the stability question, and spent an entire 4 weeks in a great deal of anxiety over my daughter's back that I could have been spared if I'd just asked at the first appointment.
I hope that helps. It is a very stressful thing when your child has a back problem! Happy to answer any more questions and provide any sort of emotional support for you here on the board or via PM. Stay calm and try not to worry. Let us know how the doctor's appointment goes.