I agree. When I saw her testifying, I only caught a snippet and did not realize that she was a defense witness - I thought she was a prosecution witness! (Thanks for the video link, I did not know her name and had been Googling trying to find her).
When it was time for jurors questions, she was asked if she ever called Arias a stalker. She replied, “Yes.” (So much for helping the defense)
Also, during the questioning, Juan showed a picture of Travis with his throat slit. Jodi's expression did not change for several seconds. It was the witness, Lisa Daidone, who started to cry and, when Jodi saw tat others in the courtroom were crying, pretended to cry herself. Again, that was far more powerful for the prosecution than for the defense.
Finally, JM treated her well and she replied with a simple yes or no. There was none of the "harsh" treatment for which JM has been criticized.