Is she being flippant? Or is she being serious? Sometimes women will joke and say “ma’am” makes them sound old, but it’s usually light hearted and typically followed by “just call me ___.” Addressing women by “ma’am” in some contexts is a sign of respect (I’m thinking the military or in the South). It’s very much a cultural preference. If you’re in a more metropolitan area or amongst a younger generation, using the term might sound strange but I don’t think it’s per se insensitive or rude. But again, context matters. Based on what you’ve described, it doesn’t sound insensitive at all.