Should I have...?

I witnessed this scene today:

- Old Uncle wanted to try bubble tea(no joking)
- Counter Girl suggested oolong tea(sensible)
- OU paid for drink (as he should)
- OU then requested to break his $10 into 5 x $2 notes (trying his luck)
- CG obliged (not bad service)
- CG realised not enough $2 notes in the cashbox, returned the $10 and apologised(reasonable)
- OU became angry and shouted at CG to return change of $0.10 (uncalled for)
- CG replied she did so earlier (unfortunately i was busy on my phone to actually see her giving back change)
- OU got agitated and called CG stupid and threw the receipt at her(plain rude)

I was 1 arm's length from the whole scene...and throughout that 5 mins, i was wondering if i should interfere..

I could have told OU that CG already returned the change but i hesistated as i really did not witness the returning of $0.10 change..or i could stand up against OU calling CG names - i really don't like this..raising voice i can still give the benefit of doubt that one has a loud voice..but names calling..tsk..

Also, i was feel a little lousy these couple of days and i really have no intention of getting into another argument, esp when i'm not directly involved(i got into an ' argument' with a condo security guard the day before and he actually called up my friend - the resident, to complain about me)

I'm usually quite mild and occasionally have been labelled 'pushover'...but the 5% when i erupt..you wouldn't want to be near me..

Sorry CG.. -.-