Hi. If you have completed the work your gig or custom offer promised, deliver.
If there’s anything wrong with your work, the customer can then use the revision button and officially ask for a revision.
You can (politely) insist that she tells you what supposedly is wrong with your work and what she wants you to modify, and if she doesn’t, redeliver until she does tell you or lets the order autocomplete.
Neither buyer nor seller can cancel one-sidedly, they can only send a cancellation request which you can reject if you find it unfounded, or they can ask support to cancel. If support will, you can try to prove to support that you delivered everything that was agreed on.
That can happen with any order, whether a customer said they dislike your work or not before.
For now, if the work you offered to do and agreed on with the customer, is completed, deliver, and deal with the potential reaction when it actually arises.
The customer might finally tell you what they want you to change, or just accept or let the order auto-complete.
The worst-case scenario of a cancellation may or may not happen, however, if you don’t deliver your work even though it’s completed, and the order gets late, your delivered on time rating will definitely take a hit.
If you completed the work, there’s no reason to not deliver.
The customer then still has 3 days to ask for a modification. How you deal with that is up to you, respectively your gig (did it include free modifications or not, do you want to do it even though the gig didn’t include any, etc.)