We had an awful experience by trusting in SWISSCARE health insurance as a basic insurer for my wife. Beside the missing acceptance as an official insurance company in several districts in Zurich as well as when visiting doctors or hospitals.
In our case, after getting treatment at the Zurich Universitätsspital emergency room, the re-insurance company behind SWISSCARE, the Europäische Reiseversicherungs AG, tried everything to deny paying the costs. They went even so far that they submitted our case to their headquarters in Copenhagen of the Nordic Health Care Insurance. All our tries to convince these companies to pay failed until we got help from the Patientenstelle Zurich. Who finally, with help of their lawyers, could force them to pay the claim.
However, you might have good experiences with all of them. Unfortunately in our case they made our life hell for over 2 years. It wasn't just the fact that they refused to pay, during the whole period of an open case my wifes health problem was seen as an preexisting condition.
Does your wife work? If she was at an ER, dpeending on what happened, it could perhaps have counted as an accident, in which case the employers accident insurance would cover it.
My experience with Swisscare sofar is good, but me and my wife didn't have anything other than the odd doctor's and medicine bill to claim sofar...
Swisscare are not a basic insurance provider and say so clearly on their FAQ. Their plans require coverage in another social security system. If you are not exempt from Swiss mandatory insurance, you can't be covered and they will try to wiggle out, as any insurer would. For that, you pay less than you would under a Swiss plan. You pay yer money and you take yer chances.
They will offer you insurance as if they were a basic health care provider. If you live in Switzerland and are only here temporarily, you, and your spouse, can be exempt from the obligation to have the basic health insurance here by the cantonal authorities, provided you have another insurance that covers you. For this you have to fill out a form and send it to the insurance company you have here, who will then say you are insured by them. Depending on your home country, that can be the insurance you had there (this is for instance France, if I am correct) or an insurance like Swisscare, tradiconsult, etc. They then say they will provide AT LEAST the same cover as the swiss basic insurance. If you have a pre-existing condition, they will probably refuse you. If they tell you now they believe your wife had a pre-existing condition, I would imagine the burden of proof should be with them. But, they are an insurance company after all, so they might try to get out of paying...