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.