No.. You can use "begin_function" attribute in the XML file to change avatar animation. Simply create a function that changes animation.
Or a better solution would be adding another attribute: "animation_name". Make a sprite with different animations for everyone, who has dialogue lines in your game, and when each line of dialogue starts set animation to "animation_name".
So your xml can look like this:
<TextLine id="1" id_next="2" animation_name="guard">Stop right there!</TextLine>
<TextLine id="2" id_next="3" animation_name="character">What happened here?</TextLine>
...
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