I don't think Chandni loved him, more she wanted to haasil him/his powers and capitalised on the spell Markaat put him under. I guess Markaat asked her to help with her plan too...but then Veer rejected her, so she was all "if you can't be mine you can't be anyone's" I guess at that point she thought she'd killed him, or at least removed his powers, so what use does she have for him now?
IRL though, she was likely just a tiny plot device to separate Vani temporarily for the shock value, and they didn't flesh her out beyond that. Even if she was originally meant to have a longer role (which I don't think she was), after the reaction they had from fans to her character/the track, I'm sure the makers thought better of bringing her back 🤔Personally I don't need or want to see her again...she was fine for that short role but there's really no desire for me to see her again any time soon.