I really don't see the point in having to translate first names. It doesn't happen in the other language courses. For me it's difficult enough to learn actual vocabulary without having to remember first names!
The Gaelic pronunciation of letters is not the same as the English. (For example "mh" sounds like English "v".) It would be more confusing to have to remember to pronounce letters differently droending on whether they occur in a proper name or not.
It's because Anndra starts with a vowel. You'll see it at other places in the course, for example with "ollamh" becoming "ollaimh" when you go from the nominative to vocative case ("tha ollamh snog" versus "tapaidh leibh ollaimh").