Yes, I do see this as Lana's interpretation of Regina's motivation. And in Regina's case it is likely to be true as well. Her anger and desire for revenge would make it pretty much impossible for her to be willing to fall in love again.

I wonder what would happen if Regina were proven wrong?

Seeing someone else fall in love again? Or falling in love again herself? Number one would likely increase her desire to destroy everyone else's happiness and number two is a possible redemption story line.