Wow - you've got a very smart little girl on your hands!
You did a great thing with the magic spray and, as you can see, it worked. However, now that the 'monsters' have been put to rest your daughter is smart enough to know that she is going to have to do something else to continue to stall the bedtime and garner your attention. Give her credit - she's intelligent enough to know how to manipulate this system and didn't just give up after the 'monster spray'.
It won't be easy but you need to stop giving attention to your daughter after her bedtime routine has completed. Tell her that tonight she is going to start a new routine. After the bath, brushing teeth, book, tell her it is time to go to bed and stay in bed for the entire night. And, after you put her in bed that is it. No more return trips, no more reassurances, no explaining to her why she needs to sleep, no yelling at her - nothing. When you give attention, be it positive or negative, you are reinforcing the idea that if she screams, begs, pleads, whatever, you are going to come back to her and give in.
After the final goodnight, leave the room and let her be. She's 3 years old and knows what she is doing, and by now you probably know the difference between the 'emergency cry' and the 'I want attention cry'. She does not need you - she needs to go to sleep. If you have to return, then go in as silent and unemotional as possible. The more you talk, the more exciting you make it for her and the more difficult it will be for her to sleep. Make it as boring as possible.
Understand that this will not cure itself in one night. It could take a week. Be consistent with your techniques, because as long as you keep going in there, giving in to her demands for your attention, and reassuring her, she will only learn that "If I scream, she will come".