I have a few questions in order to help you properly.
What will be your total income for the year? Do you have income from any other sources?
What is the federal tax withheld to date?
What is your filing status? Do you have any dependents?
Do you itemize deductions? If so, what are your deduction figures?
Unfortunately, her income is too much for you to claim her as a dependent, so you will not qualify for head of household.
It would appear that you are going to be responsible for approximately $12,811 in federal taxes and approximately $2,570 in NJ state taxes.
Depending on how much taxes are withheld in the last month, which I estimate to be an additional $840, you are looking at a federal balance due of about $2,736. NJ state is harder to estimate, however, it doesn't even look like you will owe $100 to NJ state.
You can contact the IRS about paying Estimated Taxes. Please view the information here: http://www.irs.gov/businesses/small/article/0,,id=110413,00.html
If you file your return and wind up with this balance due, you may be subject to penalties and interest.
I put your income through a W-4 Calculator on hrblock.com to figure out how many dependents you should claim through the year. You are safe to claim 2 dependents on your W-4 and have $1 withheld from every paycheck, if you are being paid biweekly. This will maximize your checks during the year and leave you with a small balance due ($13).
Please let me know if I can help you further.