I don't even know where to start with this email. You should not have to ask this type of question - this is the questions that your clients ask you. My suggestion to you is to go work for someone who can mentor you and teach you. We can only help you so much. As for the answer to your questions:

1) have taxes withheld from social security

2) increase the withholding on her W-2

3) make estimated tax payments based off the dividends and capital gains.

4) proseries estimated tax worksheet will help you and tell you what the estimates should be based on the current year. 

Good Luck.