As regards the inheritance, as you say (currently) it's under the inheritance threshold, so no tax.
CGT doesn't apply to the actual inheritance 'transaction'.
If she then immediately sold the house, without ever living in it, CGT would apply to any increase in value between the value declared for probate (IE the will) and the price she gets for it. EG if the house sold for �10k more than it was valued when she inherited it, CGT would apply to the �10k.
But if she moved into the inherited property, CGT would then not apply at all. I don't know if there is a qualifying period - I don't believe so. It just has to be the 'main' residence.
So, in essence, no, she won't end up homeless. At worst probably a few �1000 down.