What you guys are saying is all wrong, you can get her to 4 hearts without even showing her the collar, read ending 3, this ending details what specifically to do which from what I've read you all are doing incorrectly. Once you get her to 4 fully purple hearts then you can show her the collar and she will become your bitch with 2 variations. 1. With her tail and dog ears or 2. In her human form. The difference is whether or not you cum inside her.
Also here is my 100% save.
Mega
After downloading place this file in the following folder. C:Users:*Whatever user*:AppData:Roaming:Macromedia:FlashPlayer:#SharedObjects:4TKC67H6:localhost and overwrite your save. All options in sex mode are unlocked including unlimited stamina for both tongue and penis.