Wedding bells and invitation!

A varsity mate is getting married soon; and I received a call from her.

She is asking me for a favor; and a responsibility which she entrusted me with.
Oh my, I could not possibly say no and yet, I am just so touched that she thought of me immediately!

Wow, I can't wait, it will be my first experience and I'd love to do it!

Any guess what am I being asked for? =)