sorry I misunderstood you.

when you said about something feeling good, you were in essence saying that there is very little meaning to the suckling part - it is just snuggling.

maybe

the thing is, it has some sort of a meaning in IT's woman's mind

this is because she allowed it at some point and even liked it

then she broke up with IT

then she partially changed her mind and said "It is OK to have sex, but we will not have a r/s." Whatever she meant (in her mind) by saying that this is not a r/s, it is clear that she downgraded IT. And, stopped responding positively to his suckling. So somehow suckling was part of the former relationship that had a higher status in her mind, but not part of the new, downgraded arrangement.

Since I do not think that she is just being randomly obnoxious, there must be some meaning to all of this in her mind. Maybe being suckled feels intimate to her ("snuggling" = intimacy) and now that she is not into having a r/s with IT, being suckled feels untrue to her. Or, something else. But not random.