Aah but what was she towing it with & was it a braked caravan.
the rules are very simple.
& I have posted the link to vosa & DoT before. but for clarity here it is below.
Category B vehicles may be coupled with a trailer up to 750kgs MAM (allowing a combined weight up to 4.25 tonnes MAM) or a trailer over 750kgs MAM provided the MAM of the trailer does not exceed the unladen weight of the towing vehicle, and the combination does not exceed 3.5 tonnes MAM.
For example:
- a vehicle with an unladen weight of 1.25 tonnes and a MAM of 2 tonnes coupled with a trailer with a MAM of 1.25 tonnes could be driven by the holder of a category B entitlement. This is because the MAM of the combination does not exceed 3.5 tonnes and also the MAM of the trailer does not exceed the unladen weight of the drawing vehicle
Whereas
- the same vehicle with an unladen weight of 1.25 tonnes and a MAM of 2 tonnes when coupled with a trailer with a MAM of 1.5 tonnes would fall within category B+E. This is because although the combined weight of the vehicle and trailer is within the 3.5 tonnes MAM limit, the MAM of the trailer is more than the unladen weight of the drawing vehicle
Also found this
]Most caravans when fully loaded will be over 750 kg. This limit can be exceeded without taking a B+E test under some circumstances: The gross laden weight / MAM of a trailer can be upto the unladen weight of the towing vehicle, up to a maximum of 3500 kg in total for the combination. e.g. Land Rover Defender 90 has an unladen weight of 1740kg and therefore you might think you would be able to tow a trailer with a MAM of 1740kg, but beware that the load capacity of the Land Rover, over 20kg, would put you over the 3500kg MAM for the combination! So as the MAM of the Land Rover is 2400kg you can only tow a trailer with a MAM of 1100kg (If your trailer has a MAM above 1100kg but only weighs 1100kg because it is not fully loaded it would still require a B+E licence). If you had a Land Rover Freelander weighing 1640kg unladen, with a 2060kg MAM then your trailer could have up to a 1440kg MAM and would not exceed the 3500kg MAM for the combination and therefore only a category B licience is required (If your trailer has a MAM above 1440kg but only weighs 1440kg because it is not fully loaded it would still require a B+E licence). e.g. If you have a trailer with a 1400kg MAM you could tow it with a Land Rover Freelander (1640kg unladen / 2060kg MAM) without B+E, but the same trailer would need B+E to be towed by a Seat Ibiza, and the actual load towed would be less as the Seat Ibiza towing capacity is only 1200kg. If your trailer is below 750 kg MAM it can be towed by a vehicle up to 3500 kg making a total train weight of 4250 kg.*
All trailers over 750kg MAM (Maximum Authorised Mass) should display a manufacturers plate with the MAM of the trailer - Remember this is the weight that counts, for driving licence regulations, regardless of the actual weight being less.
]If your trailer has not got a manufacturers plate showing the MAM you should not exceed 750kg in total (trailer + load).
I appear to have miscalculated the max weigh as it's 1100kg for a 90.