What does adding a qualifying relative do for my taxes?

Adding a Qualifying Relative increases your Personal Exemptions by $3900.

However, if your income is too low, it won't make any difference.

It's supposed to change sometimes. It's not supposed to change always.

The purpose of claiming her is to see you are a person whom it would help. It didn't change, so you're not a person whom it would help.

depends on how much tax you'd have paid if you didn't claim the additional dependent. If you already had no tax, and were getting back everything you paid in, then adding a dependent wouldn't add to your refund.

Most times it would help, however you would need to provide more details on your situation in order for someone to determine why it didn't help in your case.

it should reduce your taxable income by $3900

It might not do anything, depending on how much you make.

This IRS website will help you determine whether or not you can claim someone as a dependent:

http://www.irs.gov/uac/Who-Can-I-Claim-as-a-Dependent%3F

Each dependent reduces your taxable income by about $4,000.

Your refund did not increase because the IRS did not accept your relative as a your dependent.