Rem wasn't fond of Light. No she was not. That slippery bastard was ruining Misa and the blonde idol was too blinded to see it. She'd tried talking with her but Misa'd been beyond reason. The only solution was to direct the blonde's affections elsewhere.
And where else was better than you?
You were a little model friend of Misa's. From what Rem had observed, you were a better option by far for Misa. And so the Shinigami had started planting seeds in the girl's head, showing her how much you cared and were gentle with Misa and actually liked her little quirks instead of tolerating them like Light did - and boy did Misa take the bait - hook, line and sinker.
Your life felt like it went straight to the shitter the moment Misa's adorations were turned on you.
Misa never really had a high regard for life - which led to her being impulsive and lack remorse when she started isolating you through writing your friends' names in her Death Note, viewing them as nothing more than removed 'blips' that kept you out of reach.
Oh how overjoyed she was when Rem reported you'd started taking medication to deal with the traumatic events around you and soon after running into her arms for comfort when you simply just.. broke down. It was all just so... delicious. It was only a matter of time before she and Rem created the perfect conditions to drive you to fully depend on her.
You'd be hers - regardless of what you wanted. You were her happiness, and in turn - you'd learn to love her too!