Vow of Silence

"Congrats on a well-deserved promotion! You've been in that position for so long."

What's the problem with a congratulatory remark? A lot, if it's actually a backhanded compliment. The above implies that your friend didn't quite earn the promotion. Instead of suggesting that anyone in her (worn) shoes would have gotten a bump at work, try a hearty, Good for you! Very impressive! suggests Melton. And if your friend suspects that she, say, got that promotion because she'd been in that job so long it would've been embarrassing not to, then leave the door open for her to discuss that with you. You should be a sounding board for your friend, not a sniper.