Duty of Care:
In this respect I think the employer can argue they've discharged their obligations in respect of this because they supplied a replacement battery. That is, they've taken remedial steps.
However, it hasn't been established that it was the battery. Though that it seems the most likely.
In terms of the advice given to her by the IT department, the employer can argue the point that quality of the advice they give depends on the accuracy, the completeness of the information she gave them. If she didn't tell them the IT support person about the battery issue, if she didn't tell them it was getting too hot to touch then yes, you can well understand the IT person would have responded with "Wait for it too cool down, the fans will cool it".
This particular part of the claim will come down to her word against theirs, now she's got a lot to loose, £100K to be more precise, so is she really going to tell the truth as to what information she gave the IT support technician?
Radiators in the home are designed to get hot, computer's aren't. Even she knows that.
You have to allow for the fact, you can't expect Joe Public to know about the battery problems that have occurred with Lithium-Ion batteries recently, BUT she's been completely stupid leaving unattended an appliance which she knew was defective, which was getting very hot and not taking adequate measures, such as turning it off, unplugging or removing the battery.
She can't absolve herself entirely of responsibility and hope to pass the entire blame on to an IT support person. The fact is, this lady knew there was a problem with the laptop, she'd even had a replacement battery, so what does she do? Knowing it's over heating, she decides NOT to remove the battery, or even suggest it to the support person and seek his advice.
She knew there was a serious problem, yet made no attempt to turn the defective appliance off, or take it somewhere where safe (outside!) and she's just trying to blame it all on some advice given to her by tech support person.
I think it could be argued that the advice given to her by the IT support tech is that it is just that, advice. The tech. wasn't there in the room to see and touch the laptop to determine the best course of action to take, the support tech. gave advice and it's up to her as a mature adult to make a decision on whether to take that advice. She knew full well of the history of the laptop and the problem's she had with it and she chose the wrong course of action.
The law expects people to have a reasonable amount of common sense, if they haven't got it, I doubt the law is going to award in favour of the person that doesn't have it. Except America that is ! I mean, what are the chances in the UK of putting a hot cup of coffee in between your legs when you're sitting in a car, driving off, it scolding you and then being able to sue because the seller of the coffee didn't write on the cup "Coffee - Caution: contents hot!"
I suspect, she didn't know how to remove the battery, how often do you change a laptop battery, hardly ever. And not being technical, she probably never figured out how to do it.
But if you own or are operating a device with batteries, then you should know how to remove the battery, so trying to blame this on to the employer would be inappropriate I feel.
But there again, she had received a replacement battery earlier, so this now begs the question, did *she* actually replace the old (and presumably defective) battery?? I bet she didn't!
If it transpires that she was in receipt of a new battery and didn't change the old one, then that can't be her employer's fault. At the end of the day, they can send her the battery, but it's up to her whether she actually replaces it.
I await with interest to see the outcome of this case, but I think the court is going to rule against her.