All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
There is no harm in applying something to the lips during the daytime of Ramadan, be it cocoa butter as mentioned in the question or other than it, provided that its taste does not reach the inside of the body. According to Shaykh Al-‘Uthaymeen :
The woman can apply cream or any other ointment to her body, and it does not invalidate ablution or fasting, and the same is true of applying it to the lips, which does not invalidate ablution or fasting, except that as far as fasting is concerned, if such creams have a taste, then they should not be used in a way which allows their taste to reach the inside of her body.
According to Shaykh Ibn Baz :
Likewise are products used to beautify the face, such as soap, creams, and anything else that is applied to the surface of the skin, e.g. henna, make up, and the like; there is no harm on the fasting person to use any of that.
Allah knows best.