She should wait until after November or early January.
Let some of poseurs dive and exit.
No later than November: HOW TO FILE FOR NEW HAMPSHIRE PRESIDENTIAL PRIMARY
How to File: The filing period will be between the first Monday in November and the third Friday in November or during such other time period as the secretary of state shall announce. A declaration of candidacy must be filed in the New Hampshire Secretary of State’s Office along with a filing fee of $1,000. Declarations of candidacy will be available from the secretary of state’s office. The information required on the declaration is as follows . . .
I'd like to see her wait until the middle of that period, but I don't think it's an option if the base gets too excited about September 3. The rather large swings when a new candidate announces (Trump, Perry, etc.) suggest that voters are waiting for someone new, probably a particular someone - and we all know who that is.