CotswoldStrife - you sound like an excellent landlord, and she does sound like a good tenant, trying to make it through some awful difficulties - it means nothing from a stranger on the internet, but that really makes you a good human being.
I would check with a plumber, but I've moved into a couple of properties that had had the gas capped for over a year (owned by a company, old tenant died, they stripped it, put it on the market, but it took a while for that to happen/for it to all complete), and another that similarly had been stripped but not finished bfore that and there were no ill effects - neither had gone into arrears, so there was no meter change though.
The first house was a 60s semi, well ventilated (or possibly that should read drafty - single glazed when I moved in) so no heating over winter wasn't an issue - it was all cold, so no chance of condensation!. Getting a Gas Safe engineer out and getting everything re-commissioned was pretty easy. The only issue would be if she was drying a lot of clothes in the house/leaving the windows permanently shut. She sounds like a sensible sort, so I would hope that's not the case - but she'll have to figure out what she's doing come winter (although, we lived for years in unheated homes, and managed)
The second place was an ex-council - 30s house, and again, no problems no damp (again, well ventilated/drafty).
Whereas I lived in a modern flat and it was a damp nightmare around the windows unless I kept the bathroom extractors going continuously and left the windows open winter and summer.
I've also spent more time than I care to mention dealing with old tenant's payment demands/bailiffs - and actually, they've all been remarkably pleasant to me once I explained the situation (that I was a new owner/tenant) - although British Gas took a few tellings! I can't imagine my tenant experience is unusual so I'm not sure I would worry a lot about that - people almost expect it, and a firm voice on the phone tends to sort it out.
So I guess it boils down to, what kind of implications do you mean?