[GGG]

You should sign pre-nups / cohabitation agreement. That can protect your assets you are bringing into the marriage

Even with one after six months you become common law and have all the liabilities of marriage.

Then you need to define things like rent. Even with a pre-nup if she is paying into the mortgage or paying bills in place of paying the mortgage she could be entitled to her share of the property she paid down and potentially appreciation of the property.

So if you do nothing and things go south she could be entitled to portions of your assets and even depending on length spousal support. Everyone should talk to a lawyer before moving in or getting married if they have assists.