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You may be able to get a gate pass to meet them on both the arrivial or departure. Have your son call JetBlue and ask if it's possible. Plan for both ways, as sometimes they will say yes, but you end up with somebody at the airport who is not so generous.

On JetBlue's Boston page they say

When a gate pass is issued, it is the TSA's decision as to whether a young child, in addition to the unaccompanied minor, may pass through security with the adult.

and

When picking up an unaccompanied minor, one person may receive a gate pass to proceed into the arrivals area to meet the minor. Please arrive at the airport no later than 30 minutes before the scheduled arrival; however, for early morning arrivals, please check the ticket counter hours.


Of course, that also depends on how strictly they follow their definition of an unaccompanied minor, as they say at 14 she will no longer be one

A child who has reached their fourteenth birthday and is traveling alone is no longer considered an unaccompanied minor.


Getting off is not really a problem, she will just follow everybody else and the signs to baggage claim and exit.

Depending on the time, there will be airline employees around to point in the right direction. If she has a phone, ask that she call as soon as she gets off the plane so they can be expecting her and not be worried if the plane is delayed a few minutes.