Yes, you might want to send the email. I think it will have good and productive effect overall, and help the speaker further in her career a lot. Such criticism, though very unpleasant and even hurtful to hear at first, opens the opportunity to self-improvement. Your act thus shows that you do care for the speaker. Much more than a person who simply wants to minimize his or her in-comfort, shy away from confrontation and leave the speaker alone and deserted without knowing that secretly the community ignores and disdain her.
As for the fact that the email is anonymous, something that have alerted many commentedcommenters here, I disagree with the overall opinion. Academia is full of anonymous feedback, most of which has the potential to be much more hurtful and cardinal than a somewhat amusing email about one's accent. I'm sure the speaker got many harsh and brutal rejections through anonymous peer review, throughout her career, and she's not going to break down because some guy decided to write an anonymous email, peculiar as it sounds. Indeed, academia itself has reserved the right offor people not"not to stand behind their own opinion'sopinions" and ideas, so that they arefeel protected that wayto speak freely, through endless forms of anonymous feedback (reviews and student's feedback, to name a few).