Spanking can show her your dominance. You have pulled her back from her orgasm (by slowing down, for example) and now you need to speed back up so she comes close to reaching orgasm again. Multiple orgasm shy girl has multiple orgasms. You should use spanking as just another tool in your sexual toolbox. Hey, welcome to school of squirt. Allow her to purge her emotions, be there for her and hold space for her.
Squirting (ejaculatory) orgasms
Getting her in the right frame of mind is an important part of being able to give her an orgasm. Never let her guess when she might get spanked by you. They either end up with a nice guy and boring lame sex, or they end up having great sex with a bad boy who.