Always delete your scriptCache.package file after adding a new script mod to ensure the new interaction shows up.
The mod typically uses a modified "Cuddle" animation. Because The Sims 3 was not originally built with these animations in mind, there may be slight clipping with certain high-detail CC clothing. the sims 3 breastfeeding mod
If installation proves too difficult or the mod conflicts with your setup, consider these workarounds: Always delete your scriptCache
The Sims 3 does not include breastfeeding in the base game; it requires a third-party "script mod" to function. How the Mod Works the sims 3 breastfeeding mod