This is a dumb question to ask the internet, but who should I pick as maid of honor?

Okay, I realize you guys don't know my friends and family, but I just need some input here.

My fiancé and I are going to get married in the US in April (he's American), and in Germany in August. I already asked my bridesmaids/maid of honor for the American wedding, and that's not as hard 'cause you get to pick a bunch if you want. But in Germany, the bride and groom each just pick one witness (typically a best friend or sibling), and that person is then involved in the planning of the wedding and also assists in the ceremony and sits with the couple during the reception. In Germany, a lot of the entertainment during the reception is provided by the guests (short funny plays, poems, elaborate gift giving, games etc.) and typically the witnesses are responsible for organizing that (i. e. if Aunt Bertha wants to play the Newlywed Game, she contacts one of the witnesses and asks if that's okay/when to do it).

I have a bunch of friends, but I wouldn't say I'm super close to any particular one or that I have a "best friend". But I've narrowed it down to two people I would like to share the planning and the wedding with:

"Luna" who I went to high school with and was friends with in junior and senior year (I'm now a sophomore in college). We see each other maybe three times a year. I like that she is also a Christian (super important to my fiancé and me) and that she's extremely excited about us getting married. No one else that I've told has been that excited. I think she'd love the whole planning thing and to be a major part of the wedding itself. She also lives reasonably close to my hometown (the wedding is going to be there). I'm uncertain because we were never super duper close BFFs -- just good friends. And (especially if I move abroad) we'll probably lose contact and not see each other until our 25th high school reunion or something.

"Sandra", my cousin who I was really close with as kids (let's say until we were 16 or so), but in the past three or four years I've hardly seen her or talked to her. I'm a little worried about picking her because she just (one or two months ago) broke up with her boyfriend of three years and is taking it really hard. We talked on the phone yesterday and it was kind of awkward and I don't know if she would be up for it or if she would just say okay to not hurt my feelings but then be sad every time wedding-related things came up. She lives kinda far from both me and the wedding location. But I already had my dad talk to her mom about whether or not it would be wise to pick her and her mom said she would be "shocked" because she's still suffering because of the recent break-up and that I should ask her on the weekend when her mom is with her.

Forgive the wall of text/thanks for reading. Any advice?

TL,DR: Can't choose between good-but-not-very-close friend who is excited about wedding and cousin who I was close to as a kid and who just got broken up with.