In pretty much her first season or so on the proper tour, she was going well in Wimbledon, then she won the US open.
So it suggests she is very capable of playing at a good level. She hasn't done much since because she has been plagued with injuries and having operations. Before that, she was showing all the signs of a good player. You can't knock someone for barely doing much when they're either having operations or on the comeback.
So the ability is there in my opinion. Now its a case of staying healthy, rebuilding her confidence and fitness and obviously being motivated to be a full time athlete.
Can't exactly call someome a one slam wonder when they've just turned 21 and pretty much been injured since the age of 19/20
The fact she has even won a grandslam at that age should be the real indicator of her capabilities, rather than judging her when she's nowhere near fully fit or when she is injured.