I'm quite excited for this. Hoping you'll add and improve on it in the future.
There are some issues with strange hitboxes and waiting around when "dropping" a hitbox accidentaly, but nothing that at least to me seems game breaking. Except for the browser version, that has some clear issues.
The game brings to mind an old game called Your Own Living Cowgirl, which I loved. Hoping to see some mechanics from that on here, such as potions or something that alters how much can be milked.
I would eventually like to see some customizing with the girl, maybe even adding balls.
Overall I think this is very promising, and actually quite fun already! Keep it up!