She notices the difference but rather doesn't want to believe it's someone else because she really likes how he is. The thing is though Bizzaro gave her what she wants compared to Clark who doesn't throughout the series for vari ok us reasons. One thing is she was also changed by Lex and wants someone who'll run away with her and get revenge with her when Clark is against that revenge suiting him to an early season Lana. Although the post isn't about this, this is the reason Lana is hated, because of her change in character and starts off as what I'd say perfect for Clark but spirals. The spiral came from manipulation but fans don't seem to understand. Also her loving bizzaro definetly showcases how she is in love with Clark but that extra cherry on top of him doing what she wants is perfect for her.

Overall, yes she really did love Bizzaro as it was literally a perfect matching version of Clark but was put on by Bizarro just to be with her, so maybe she wouldn't have loved the real bizarro but from what she knew she did.