I haven't found out yet.
Maybe because it's exactly RM24k? Or maybe they didn't take into account the fixed allowance.
Better to wait until her salary is a bit higher.

Alliance have their own weird criterias of approving credit cards. When I applied for the first time, was rejected too but tried again a year later and was approved recently. Salary was more than 2x the required amount

That is possible. When I applied for the first time, I had a few more credit cards which I subsequently cancelled. If you have any existing balance transfer, that would also affect your application.

In my opinion, each bank has their own way of deciding whether to approve or reject a CC application. Unfortunately, this information is classified, so we can only make guesses about their criteria.
The best you can do to improve you chance of getting approved is to maintain a good credit history. Make sure you pay your credit cards in full every month, and make sure you don't have any outstanding balance on any of your loans (e.g. PTPTN).

However, even with good credit history, it's up to the bank to reject your application, so there is also an element of luck at play.

Yes, you can, though I didn't do it for my card. Refer to the FAQ for more info. http://youniquecard.alliancebank.com.my/Yo...e_faq_v1.0.html

Statement cycle

Yes. Everything.