A story of mine has the following sentence:
Alyssa was possessed by a sudden, fierce urge to snatch the teacup out of her sister's hand and dump the contents into her perfectly arranged hair.
On further reflection, I realized this sentence is ambiguous: I never said which of the two gets the tea dumped on her head. Except, I'm not sure that the sentence really needs fixing - it wouldn't make sense for Alyssa to get mad and dump the tea on her own head. (I tried to replace the pronoun with her sister's name, but the resulting sentence just felt... clumsy.)
Is there a way I can objectively tell if an ambiguous sentence will cause confusion and needs to be fixed?