You barely owe the person a “Congratulations”, let alone a gift, and it’s silly of grown adults to have such expectations from professional colleagues. This is a brand new acquaintance, so a nice “Happy Birthday” said to her is quite sufficient. Save your gifts for your actual friends and family, not fake friendships at work.

Something generic and inexpensive should be more than enough. A scented candle, picture frame, calendar, or desk ornament with a nice card should be plenty.

I always get flowers for people when I’m in that position.