I have been asking myself this same question for longer than I have been in this practice, for longer than I have understood exactly what I was asking. For me, it took the complete dissolution of the relationship for me to be free enough from the connection to see the difference between love/care and attachment. I see now that my attachment was based in a genuine, boundless, natural, fully wholesome bonding, one that I can see I still have. What built attachment on top of that sense was asking for meaning and getting answers from my unskilled mind: fantasies of "holding each other forever", marriage vows, being the cure for each other's scars, etc. Having a vision for a "fulfillment" for that sense created all manners of grasping and aversion which lead to great suffering, not the least of which was supporting the other person in some of their worst traits, because a less-than-wholesome connection was closer to the vision than no connection at all.
Now I can see that this sense can exist independent of anything else. It is just a sense. Yes, a powerful one, one that while it was being fulfilled by being in a dedicated partnership with the person created the greatest levels of joy and contentment that I have ever known. But now it just is, on its own, and that's ok.
How can we truly define a thing as "bad" without getting to know it first? Like the thief who steals bread to feed their starving children, we must engage in order to know the full picture before we cast judgement. Attachment is there for a reason. Everything is there for a reason. So we just need to find the reason.