Awww bless you, i'm not in your position yet as my son is only 5 - but still...i drove to Luton the other day (in a newly acquired 1.0 litre Nissan Micra
) whilst he was at school and i felt jittery, both for leaving him so far behind and for having to go on the motorways!! (M1, M25)
I have to admit, they're pretty scary places.
I passed my test 18 months ago and i've only 'done' the Motorway three times.
But, as you say, your daughter is a confident, headstrong young lady..who seems to have a good head on her shoulders.
I'm sure she'll be fine..maybe she got caught up in traffic? I would expect they stopped for a break too, 5 hours+ is a long old time behind the wheel.
There tends to be more traffic when the weather is awful as everyone drives. It's calmed down a bit here, we had the worst of the weather this morning.
Let us know when you hear from her - and in the meantime, have a nice cup of tea or a glass of wine and relax.
xx