Her nose could had been damaged when she fell, Solar found Wendy laying face down iirc and rather then reconstructing her old nose they probably just made it how it is now again we don't know exactly what happened but we know she had major trauma to her face so obviously stuffs going to change
If she would had never fell she more than likely would had kept her old face
Idk, with her history with cosmetic procedures and having a period of time off-the months needed to fully heal swelling, bruising, etc and let the surgery settle I kind of think she probably too the opportunity to get it taken care of.
I think RV with fan meets, touring, solo work, Korean festivals, comebacks, Japan debut etc have been swept off their feet between mid 2017 to 2019 and she had no time to get any invasive work done and having practically a full year off gave her ample time to refine her look and heal up in peace.
The fall also provided a good alibi so to speak, kind of like when Yuju took a hiatus and stayed out of the public eye for a few months only to comeback with plastic surgery.