For those visiting Chinese friends this week, especially on Saturday, remember to say, "Happy New Year" or "Happy Spring Festival". (Vietnamese celebrate this festival, also.) If your so inclined, say, "shin nee-an kwai le". Don't be afraid to butcher it, as the ladies get a good laugh at it.
If you want to give her a gift, a red envelope with $88, eight crisp tens and eight crisp ones, is best. Or, leave a good tip plus the envelope with eight ones. (Eight is the luckiest number.) Party stores often have the envelopes. But, they may be sold out.
Do NOT use a white envelope. White symbolizes death. Four symbolizes death, as well. So, four 20s is bad. Be sure to use both hands, when presenting a gift. And, do not insist that she open it. This is bad luck.
This has been a Public Service Announcement.