If I had to guess, Macy's has probably flagged your wife's account for some reason or another. I'm sure that somewhere in the system it allows the credit representative to do such a thing. Unfortunately I don't have any advice as to how to get to the bottom of this perdicament. Perhaps a call to someone in corporate (and not just the regular CS, and not just the backdoor number) might be something to look into and research.
FYI, I've been a proud Macy's card member since May '08. I've had three GLI's since then (never asked for any of them) and originally had a $400 limit that's now up to $3200. I've never had a balance over $500 and it still revolves around that each month. I make at least two payments a month, at least one online and one at the store, and usually have activity on a monthly basis. I called in a week or two ago to inquire about my Star Rewards history (to see how much I've spent at Macy's this year) and the rep gladly gave me my 3rd GLI, and I didn't even ask for it! She also told me I'll be due for my next GLI in May.
Pappy, I am puzzled, really.
I will say that maybe it has to do with the initial? I know Best Buy has two programs, and maybe Macy's does, too? My initial CL was $800.
You probably mentioned this already, but have you tried actually going into a brick and mortar Macy's and asking CS there to help you?