Should my x's girlfriend be texting my eight year old daughter?

I gave my 8 yr old a cell last summer so I could keep in touch with her while she was away from me. The x's gf text my child and I asked her not to, it was for emergency use and for me and my child only. That was months ago. She text my daughter again telling her how much she and her daddy missed her. (Just yesterday.) BARF! I replied to her again asking her not to text my child. She goes on and on saying she thought it was for emergencies only but it wasnt that way this past weekend, (It was dads weekend). I told her flat out it was none of her business when and why my daughter and I text eachother. This woman does not like me and proceeded to call me HORRIBLE names and threaten to call the police on me. I would say she is the one starting trouble knowing how I feel about her, (its no secret I dont like her) and she just wants to start crap with me! Anyway, this happens about every six months. She does something or says something to try and get me upset. I have gotten to the point where I just laugh and stick it to her. IM NOT MEAN!! I just tell her some facts that she doesnt know I know. OH GOSH! How High School is this?!?! Typing this makes me feel so stupid! I just want her to leave me alone, but she seems to like to start problems with me! I think she is miserable and jealous of me, but that is just my opinion! What do you think? I dont see any reason for her to be texting my daughter. They are not close and only sees eachother every other weekend.