She shows expenses for herself. Alternatively, you can sponsor her, so your bank statements shall be attached then.
There's no need to maintain balance, but putting 2 thousand pounds in her account just to make her savings get past the reasonable threshold would raise eyebrows.
I wouldn't really use credit card as a valid proof of funds. If there's no money in the bank/salary transfers/etc, having a credit card won't help, as they're not your money, essentially - it's the bank's money. You can add it to the documents, but they're more to strengthen the case additionally, assuming financial requirement is met already.
Not a qualified immigration adviser. Use links and references given to gain confirmation and/or extra information.