There aren't yet any treatments, including any FDA-approved medications, for MCI. There's some evidence that donepezil (Aricept) can slow the progression of MCI to Alzheimer's disease in people with amnestic MCI in the short term.
If someone is indeed found to have MCI but not Alzheimer's or another form of dementia, her abilities may not decline any further. But at least you have the advantage of having had a distant early warning so that you (and her physician) can monitor her behavior and make appropriate plans in the event of further decline.
She can also take steps to cope with memory problems. Depression is often found in people with MCI, although it's unclear whether the depression causes the cognitive decline or the other way around. Treatment for depression may help her cope with the changes she'll be facing.
