So when recieved she can just send a letter stating it was out of date ?
Er...no.
Only the first NIP (to the Registered Keeper) is subject to the 14 day rule. In fact it's the only one required by law at all. Any subsequent NIPs are provided as a courtesy, but mainly because they are usually printed on the same sheet of paper as the "Request for Driver's Details".
Although on the same sheet of paper, this request is a separate document which is subject to different rules. In particular it has no time limit. Your daughter must respond to this request. If she does not she will commit a more serious offence which carries six points.
Back to the NIP, as above, the rental company is unlikely to be the RK. If your daughter wants to consider defending the speeding charge on the basis of a late NIP, she must find out who the RK is and when they received their NIP. Only if that one did not meet the 14 day rule will she have a defence to the speeding charge.
55 in a 40mph limit is too fast for a course and he should be offered a fixed penalty (£00 and 3 points) provided she has no more than eight "active" points on he rrecord.