Hello jenmaries,
1) Generally, there are two 1040's that can be used: the 1040 in your link, or a 1040EZ. There are no special 1040's for overseas Americans.
2) It's the calendar year, 1 Jan. to 31 Dec. (and no apologies needed).
3) Depends on your decisions on 4).
4) She may have to file 1040 Schedule B. If she had NO accounts in the UK (or elsewhere abroad), including joint accounts, then she would fall under the $1,500 level required for reporting and would only declare the interest on 1040 (please read the instructions for Sch. B for other qualifications). If her name is on any account in the UK, including joint accounts, then she must file Sch. B, and particularly Parts I and III. If the aggregate value of all foreign (to the US) accounts with her name on them is over $10,000 (total value of account, not just her half) she must file TD F 90-22.1. If she does not want to be taxed by both the UK and US on the same income (no one does), she will need to file either, or both depending on circumstances, Forms 1116 (credit for UK taxes paid) and/or Form 2555 or 2555-EZ (exclusion of UK income). Form 2555 comes with requirements on Residence or Presence Tests which may require filling for extensions. You need to have a read of the 2555 instructions to see how you want to proceed. You do have other options, such as filling the 1040 now, paying the taxes, and once she qualifies for 2555 filling a 1040X to reclaim the taxes paid.
And before anyone jumps in, please pardon my non-PC language.