Here's the breakdown of why and how to correct it:
* "Elle appelle" means "She calls."
* "Comment" means "how".
To make a correct sentence, you need to add a direct object to the verb "appeler" (to call).
Here are some possible corrections:
* "Elle appelle comment ça ?" - "How does she call it?" (referring to something)
* "Elle appelle comment son chien ?" - "How does she call her dog?"
* "Elle appelle comment son ami ?" - "How does she call her friend?"
* "Elle appelle comment la situation ?" - "How does she call the situation?"
Essentially, you need to specify *what* she is calling.