Yes Prue and Andy were cool together. Thats why I talk about their relationship in some of the chapters so readers know about the the Charmed ones past in my stories too. I think Prue and Andy's relationship is told by both Prue's from both Charmed families.
So then readers know where both Prue's got to where they are in my stories now and how their relationships changed after Andy. Evil Prue is the only one who got married to Andy. The other Prue only went out with him when they were both younger as she found someone else to marry. Andy still came back into her life though and was still killed by a demon. They were just close friends instead for the year he came back into her life.