Weddingbee boards

Okay - this is copied from my vent post because I need actual help on this topic:

I chose my FI little sister who is going to be 20 as one of my bridesmaids.  She has never been in a wedding before (strike 1) and lives in the dorms at college on the other side of the state (strike 2).  For those two reasons, I asked her but knew she wouldn't be super involved, which I was okay with.  Asking her was a big deal and something that I know meant a lot to her.  Basically, buy the dress, fly home, show up at the rehearsal and the wedding.  Not a big issue.

Today, we got a call from their Dad about the wedding.  It's 9 months away still, and his sister called Dad to apparently have a meltdown about being in the wedding.  She is worried about everything - getting home in time, participating, etc.  When FI got the call his Dad basically was questioning our reasons behind picking "such a hard time for people to be there."

He told his dad flat out that it was $1700 cheaper (venue and catering costs) than if we had chosen a Saturday.  Dad was surprised (why!? my FI has even been married before - everyone knows it's pricey!?)  Whether or not she is IN the wedding, she will end up flying home for it.  Dad can afford her flight, her dress and anything she needs so this wasn't a financial freak out.  She has time to arrange her class schedule (and I know she can get classes early on Fridays), ask her professors to work with her, etc.  We go to the same college (I'm in a distance program) and it isn't midterms OR finals for her.

I'm planning to email her and talk her off the ledge - Does anyone knwo what I should say to her?

I'm confused. What day is your wedding?

Sorry about not mentioning the day!  I have to laugh at myself assuming everyone knew what day my wedding was!  :)  Yes, it IS on a Friday night.

@Crazy Bee - Yes, I think it is a case of her really not having any idea of what our expectations are.  I've actually been directly delegating to my other bridesmaids exactly what I need from them and haven't asked anything of her.  So I'm planning to shoot her a quick email and give her the scoop.

@SapphireSun - Without knowing what her class schedule will be yet, I'm not sure if she can still attend class and make it that night.  And not to sound selfish, but if you are going to be in the wedding, I feel like at the very least she needs to be able to commit to making the rehearsal the night before and be there the entire day of the wedding.  Yes, this means she will be skipping classes for possibly two days - however, she will be a junior next fall - this isn't "new in college" nervousness.  She has ample time to set her schedule to the best of her ability and email her profs in advance to see if missing either of those two days is going to hinder her ability to do well in class.

I'm not unsympathetic to her plight, but it IS my fiance's sister - therefore whether she is in the wedding or not, there is no way she would miss this for the world.  She will be flying home and back, on their Dad's dime, so I'm jsut lost as to why this is such a big deal - and why we are worrying about it so far ahead when none of the variables are known yet.