Um, just how did "I" change to "my sister"? You asked what YOU could do.
Your story is collapsing.
Emoticons are nothing more than text strings. or is a smiley face
while ;-) is a winking smiley face and so on. I sometimes add >;-> as a
devilish wink with evil grin but haven't a clue if it's really a standard
string. They're just strings. You don't need any add-on or even
auto-correct to add smiley face strings to your e-mails.
While you might light to see cute little graphical images displayed in your
e-mails as you compose them, you have no control over how the recipient will
see them. They may only see them as text. The recipient might be reading
their e-mails in plain text format. Even if they render HTML-formatted
e-mails doesn't mean their choice of e-mail client will show the smiley
strings as graphical images or the same ones are used in their e-mail
client. You seeing a smiley face image will not force the recipient to see
an image or that same image.
So when you sister gets an e-mail with:
"Aren't my kittens cute? #;^>"
which shows some lions ripping apart a gazelle to chow down and where the
smiley represents someone with matted hair, winking, long nose, and devilish
grin, do you think your sister will really understand or appreciate hearing
Just how do you think a graphical image (if there was one) that represented
these text characters would be represented by a sound? You think there are
enough sound bites available to be distinct from one another to encompass
all the possible strings used for smilies?