Legal Question in Legal Ethics in Pennsylvania

Can you force her? No. She will have to check with her insurer to see if you can be added (some companies do not allow you to enroll outside the open enrollment periods) and what it will cost. You will then have to compare whether you should get COBRA or another policy or go with your wife's policy.

Know however that if you need medical care that she may be liable for the cost of such care under the PA docgtrine of necessaries codified at 23 Pa.C.S.A. � 4102 - Proceedings in case of debts contracted for necessaries:

In all cases where debts are contracted for necessaries by either spouse for the support and maintenance of the family, it shall be lawful for the creditor in this case to institute suit against the husband and wife for the price of such necessaries and, after obtaining a judgment, have an execution against the spouse contracting the debt alone; and, if no property of that spouse is found,

You and your wife may decide that adding you in the long run will be cheaper than risking her liability.