When she speaks about a particular situation or event, that situation will eventually proceed to reverse itself, through whatever means possible. If she speaks about an attempt to achieve a goal, it will fail in some way. If she speaks about something bad occurring, it will be resolved in some way. Due to this, she tends to not speak too much and always chooses her words carefully. Note that it is the situation or the event she talks about that will be reversed in some manner; it is not that the opposite of what she says must occur.
But then if she talked about Clownpiece never coming back, would that make her come back again?
*scrub scrub* *squirt squirt* *squirt squirt* Okay. *wrrrr* *wrrr* Don't ever come back, OK? Sagume's using her ability to ensure Clownpiece will come back and play.