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Two part answer because you have two issues - the forms itself and where to report what.

1. The part earned while alive should be on her return and the rest on the estate. However, she may not have earned the interest at that point if she had not died. Then you could argue it is all part of the estate since it was transferred and interest received after her passing.

2. Another factor is the estate or her SSN on the 1099: 

• if it is the estate, I would put it all under the estate. 
• If it is her SSN, then you will need to: 
• make the estate portion nominee on her personal tax return -create a 1099-INT for the estate from her, see General Instructions for Certain Information Returns

I am very sorry for your loss.