I think Angel is her true love, and I love Spuffy too and believe there was a definite intense connection there, but as who she should be with I voted Riley as Riley's the only one who loved her and who could allow her to have some semblance of a normal life.
She could never be with Angel or Spike long-term because of all the vampirey complications, but with Riley she could. And in Into the Woods she did realized he was, or could be, the One.