You finally got the wedding invitations addressed, stuffed, and mailed. Now you can relax. Oh wait, your childhood friend who you haven't seen since middle-school graduation asked someone for your phone number and texted you, wondering why she hasn't received her invite yet. Um, because we're so distant you didn't even have my phone number? You also hear the same question from family members (twice removed) and coworkers: Why wasn't I invited? They're confused, hurt, angry. What should you tell them? Whatever you decide to say, do it with kindness and respect. Even if you consider it far-fetched that this person would think she should've been invited, don't bring that up. Treat her as you would someone who you did want to invite but circumstances got in the way.
Here are some suggestions for breaking the news graciously, one of which should come close to your situation.
It's the budget.
Briefly explain that, as much as you would have liked to invite her or him, your budget is tight and you had to trim the guest list. Don't get into specifics like the guest count or meal costs. Promise to get together after the honeymoon.
You're planning a small wedding.
Tell her you're not doing the typical 150-person-seated-dinner-live-band type of wedding. You've always dreamed of an intimate affair with just close family and friends. It's going to be a very understated wedding.
The venue is strict about the number of guests it allows.
You signed a contract that limits how many guests are permitted, so you unfortunately had to chop the guest list way down. If she asks who else was cut, tell her you'd rather not and leave it at that.
Your parents insist on family first.
Mom and Dad are paying and they're wanting you to invite mostly relatives. Since you and the groom have big families, you can't invite all the friends you have.