The original post is vague at best. She states my 'insurance' sent me a letter? The 'company' (maybe) ...And 'an appraiser' said she needs a new roof? I've never heard of an insurance appraiser. I've heard of insurance adjusters and real estate appraisers.
More informantion is needed. If she 'has' a policy, as far as 'I' know they can't cancel her for having a (in their opinion) worn roof. And insurance companys don't routinly send out people to check out the homes they insure every year. That would be cost prohibitve...
OTOH, If she's looking for 'new' or replacement coverage and getting a quote, they can do an inspection and turn her down for coverage if the home is not up to par.
(I'm a 20 year life an health agent who's also been licensed as a property and casualty agent.)