If your son isn't that bothered OP, then get him to tell her he's changed his plans and is going somewhere else before coming home, so there's no point her coming up to collect him. Then he and his friends can get the train home.
Does she have a black box for her insurance OP? As if she has, she'll likely have her insurance withdrawn if she's driving too fast/badly. Possibly even too many hours. Here's some info:
An insurance company might withdraw coverage from a driver with a black box if the device records repeated speeding, erratic driving, or other violations of the policy's terms, potentially leading to a cancellation or increased premiums.
Here's a more detailed explanation:
Repeated Speeding or Erratic Driving:
If the black box consistently detects speeding, harsh braking, or other risky driving behaviours, the insurer may consider the driver a higher risk and cancel the policy or increase premiums.
Violation of Policy Terms:
Some black box policies include specific terms and conditions, such as mileage limits or curfew restrictions. If the driver exceeds these limits or violates other rules, the insurer may cancel the policy.
Non-Disclosure:
If the driver fails to disclose relevant information about their driving history or other factors that could impact the risk assessment, the insurer may cancel the policy.
Tampering with the Device:
Tampering with or removing the black box can also lead to policy cancellation, as it could indicate a lack of willingness to comply with the terms of the agreement.
Mileage Discrepancies:
If the insurer detects that the driver is driving significantly more or less than the agreed-upon mileage, they may cancel the policy or increase premiums.
Driving at the wrong time:
Some policies may have a curfew, during the hours of which you may be penalised for driving.
Not attending a subsequent inspection appointment:
If you do not attend a subsequent inspection appointment your Insurance Policy may be cancelled.
I think now that you've made it very clear that she is just trying to prove how clever she is, by planning this extremely long drive, and that she's also likely to go out with your son and friends, rather than getting sleep in between journey's, I think in your shoes, I would tell her she cancels the trip, or you are going to sell the car. No argument, and mean it!