Mild Macron Mystery

I've been asked to change a customer's last name, replacing the e in her name (Scimena) with ē, as she puts in her signature.  When Development users tried making this change in the client, it would seem to save, but would be back to its original spelling on subsequent searches. I had the same result when attempting to change it on the back end.

In my [Google] research, as I've never seen that particular character used in surname spellings, the only place that character gets used is in the Latvian alphabet, which would be fine except that it would seem that the name Scimena is Italian in origin. Thus, my initial conclusion is that the customer simply uses it as a phonetic designation to help people pronounce her name properly and is not necessarily supposed to show up that way in any official correspondence. Furthermore, I also conclude that the system, being configured for US American language specifications, doesn't recognize that character as being "legit" and ignores the change.

So, do I seem correct in my conclusions, or is there some way to get this character to show up as requested? Mostly I'm looking for confirmation of my theory, but if it can be easily done, I'm happy to give my Development user what she wants.