Maybe you approached the matter in the wrong order ;) Your better half is right and she probably wants a nice wedding with a church ceremony, etc., which is not something you just throw in casually, BUT: you can also celebrate later if absolutely necessary, and you just have to soberly admit that you bind yourselves much more through a house and children than a marriage (legally) ever could. If neither of you has massive debts or any widow’s/widower’s pensions, or alimony from previous relationships, then why not get married? Getting married is relatively inexpensive and secures both of you best. Everything else is just significantly more complicated and expensive (both now and in the hopefully not occurring event of death).
Sorry for being so unromantic, but you seem to be considering this anyway. Then it should also be your option 1. Only if that is not feasible would I deal with partnership agreements, wills, inheritance taxes, etc.