Whas my friend hacked?

my elderly friend (Ann) is on a Apple group text with high school classmates. When she sent a text to the group recently, immediately someone who was not a member of the group sent a disturbing message in reply to her message , but appearing to come from my friend (Ann). My question is what can done about this, should she be concerned that somehow this person has hack into her phone. Would appreciate any help

[Re-Titled by Moderator]