This question isn't really for me, although since I have a few

Chase cards, I am now certainly interested.
My friend called me this a.m. all upset. Chase had sent her a letter saying that because she hadn't been making more substantial payments, they were hiking her interest rate from 8.9% to 24%. She has always made more than minimum payments, and she has NEVER been late. I think she's had Chase for 2 years. She has other credit cards (AmEx blue, etc.) that she has also never been late on, and has made more than the minimum payment each time. She called Chase and they told her she needed to be making more substantial payments, and even if she paid off the balance in full today, she couldn't keep her 8.9% rate. The first year, it was a 0% card. Then it switched to 8.9% fixed.
She's frantic. Does anyone have any advice, insight, or experience I can pass on to her?