Your realtor is incorrect. Just because you have mortgage insurance does not mean that the insurance company will not seek to be reimbursed by suing you for the deficiency (amount paid out). Deficiency judgments can be settled for pennies on the dollar. However, not all insurance companies or lenders will be willing to work with you and they could proceed with collection action. If you have been denied for a short sale and deed in lieu (I assume you do not want to keep the house) than you do not have any other options. It is also possible that they will not seek a deficiency judgment against you. We have had many clients that had homes foreclosed on and the lenders did not pursue deficiency judgments. In sum, hopefully you get lucky and do not get sued. If you do, lenders often are very willing to work with you on a settlement.
Your realtor is neither correct nor should they be dispensing that type of advice. I would suggest that you review this matter with an attorney in your area.
Neither the foreclosure nor the FHA PMI guarantees that there will be no deficiency suit. A local attorney with experience might be able to give their advice on the likelihood that it will be pursued.
Also consider the effects of a potential "write-off" of the debt with the failure of Congress to extend debt forgiveness income associated with mortgages on your residence.