Review the three conditions of mortal sin.

1. Grave Matter
2. Full Knowledge
3. Deliberate Consent

If these three are present in the case you describe, you’ve given scandal and must get to confession.

Perhaps you don’t differentiate between giving scandal and taking scandal?  One can commit the mortal sin of taking scandal without anyone sinning in giving scandal.  Let’s say you uttered God’s  name carelessly by weakness.  You didn’t plan it, didn’t want to offend anyone, didn’t want to offend Our Lord.  Then it’s a venal sin.  Apologize to those who heard you, make an act of contrition and pray the divine praises.  Mention it or not in your next confession.  It’s over.  

But let’s say one person who heard it acts as if you’d committed the grossest blasphemy in his presence and your apology was insincere, even mocking.  This person goes about moping, and miserable, mistreats everyone around him, says he’s going to commit ѕυιcιdє and it’ll be on your conscience, goes to the shrink and sues you for his treatment costs, quits practicing his faith, quits his job, divorces his wife, and she ends up losing the children to CPS when she becomes homeless.  And it’s all your fault!
Okay, this is a little overblown, but you get the point!  This man has committed the sin of taking scandal, but you are not responsible for having given it.  Someone who deliberately overreacts in such a manner to get sympathy, money, an excuse to be a lazy bum would have found another’s fault, real or imaginary, if you hadn’t been in the picture.  (Think of the behavior of a certain group of people going by three letters.)  
I hope this helps.