what is my child's name?

Ask the child which. Are she prefers to be known by. And realize children sometimes change their preferred names as well.

What I want to know though is which name is her first name? In the information packet it says her name is Ramar Mithushalini but is referred to as Mithushalini in the rest of the packet. I know in some countries the last name is first unlike in the United States where our first name is always listed and spoken first.

I'm afraid I may have referred to her in my letter to her by the wrong name and don't want to offend her or her family.

@Joy
I'm not staff so can't look that up for you, but just wanted to say that I have a lot of kids and have accidentally called them by totally different names before (like calling my little boys by one of my girls names etc. ) They've never been upset or offended.  If anything I've heard kids say that their favourite parts of sponsors letters are the mistakes, makes their sponsors seem more real to them haha.  And often in countries that reverse the names the kids go by both names equally.  Sri Lanka the names rarely even get translated the same, they don't have English characters.  For example, my name is Teresa but my Sri Lankan girls letters for the past 9 years have all called me Thireshka as that's just how it translates... meaning your child may not even notice or know what you call them.  Chances are "Ramar" and "Mithushalini" are both way different in her language but her languages names are untranslatable to English because the characters used in their alphabet do not have English equivilants if that makes sense.  
But hopefully Compassion will be able to tell which is the preferred name for you when they answer shortly. 
PS: I have had kids change names over the years (not that uncommon) or start signing by a different name/nickname too.  Usually when I write I just ask what they want me to call them or start addressing them the same way they signed their last letter.  

Hi Joy! There are many ethnic groups in Sri Lanka that place names in different orders depending on the traditions of that group. In your child's case, we have her preferred name listed as Mithushalini, which would be the name that she goes by. Most likely, this is actually her real first name. Ramar could be the name of her father or her family's last name. From the letters I see written to her previous sponsor, I do see that she signs them with Mithushalini, indicating to me again that this is her first name. It is a good idea to use the name your child goes by in her letters, and I would still encourage you to ask her about her name in your letters :). You never know what kind of information, family and cultural, you may find out through her answer!

Thank you Sarah. I was just confused by the information in the packet as there was no explanation on which name was her given name. I'll wait for her to reply to me.