I spell my name with one S

Hello.  My name is Marisa.  Not Marissa.  Not Marrisa.  Not Marrissa, or even Morissa, or Marysa, or hundreds of other ways to spell my name.

Marisa.

Now that you see it spelled out in front of you, don't you think if you were writing to me, you would know how to spell my name?

Well, not a certain facebook friend of mine.  She'll comment on a post of mine, or a status update, and say things like, "Marissa, you are too funny."  I appreciate the sentiment...but my name is right there....RIGHT THERE!  You can see how I spell it.

It's getting on my nerves and I don't know how to tell her.