Can Goat's Rue Really Increase Breast Tissue?

No, the only thing that is safe and consistant to increase your breast size is FDA and health canada approved breast implants

This compound is not FDA approved and I would be exceedingly careful prior to taking non FDA approved supplements.  I am not aware of any lotion or potion that non-surgically increases breast size.

Goat's rue, an herbal supplement, has never been shown in any scientific literature to have any benefit in increasing breast size.  As with all herbal supplements, there are potential side effects, and you should weigh the chances of having those against the chances (likely zero) that it will increase your breast size.  Not great odds in my opinion, I'd pass on the goat's rue, at least as a remedy for small breasts.

Almost certainly not. There are no studies that show such a benefit. As to side effects they seem mild, and are related to glucose metabolism and can interfere with insulin dosing. All the best.