Get Michelle & Dave home

My name is Leanne and I am looking for some help for my sister & her husband who are currently stranded in Mexico.
Michelle & Dave were married in August 2016 and after an amazing day headed off to Mexico for what they thought would be an experience of a life time.
Unfortuneately that wasn't the case and after just 4 days Michelle was taken to hospital and diagnosed with PAD (Pulminary Artery Disease), which through a catalogue of errors by both the hospital and her insurance company has now lead to DVT (Deep Vein Thrombosis).
They bought the insurance through payingtoomuch.com they actually hold the policy. Michelle called in July to upgrade the annual policy to include Mexico and was told she was already covered for mexico but not America. The insurance company have continually looked for ways not to pay out and made a catalogue of errors. If they said on day one she wasn't covered when she had a fit to fly letter she would have got on the first flight back home. However they e mailed to say they were upgrading her to business class on way home due to diagnosis of PAD. They then dragged their heels for 4 days by which time it had turned to deep vein thrombosis. If it wasn't for their catalogue of errors she would have been back in the uk. Then 15 days in when their flights have already left they informed them she was not covered and won't pay any further medical bills accommodation or flights home.
Fear not this is not the end of it for insurance company, underwriters or emergency assistance line.
Michelle & Dave are now stranded in Mexico with limited funds and don't know when or even how they will return home.