Co-Worker/friend text messages are usually much more relaxed grammatically - modern abbreviations used, smiley faces etc, little or no punctuation, capitals often not used for names etc. Depends how well you know the Co-worker/friend also - you wouldn't swear or use close terms such as 'love, honey, babe, sweetie etc' if you were mere acquaintances rather than good friends! Go with the flow when texting, just maybe still be a little aware ;-)
hope that helps xxx
