As a married couple payments would not matter, but as a CL couple she would have to prove unjust enrichment.
Yours is a long CL relationship and I think that if she can show that she contributed to some form of upkeep or maintenance she may win a claim against the home.
However, you too would also have to prove you no longer live as CL, but rather as "room mates" and she is not helping with expenses.
If she did things around the house like gardening, cutting grass, cleaning and cooking inside the home, she could easily sway a judge to award in an unjust enrichment claim.
Are there any children of the union?
This would be a huge factor for CS, or if she came into the relationship with children of a previous relationship and you acted in ever sense of the word as a parent, she could win a claim for CS even if there is another order for the Bio father.
Just some things to consider and research.