Belle fell in love with the Dark One because she could still see there was good underneath the darkness — she could see Rumplestiltskin — and they even shared a kiss of True Love that proved her hope was not unfounded. Similarly, Regina can see through the outer layers of darkness and knows Emma is still there. There’s still good inside her and Regina wants to help her rememeber.
It’s really saying a lot about a certain other relationship on this show when it’s Regina who sees the good in Emma and not her current boyfriend.
Does that mean the true loves kiss would be between Regina and Emma?