Is it rude to ask someone if they’re straight?

A family member’s gf asked me randomly if I was dating. She does not know me that well personally. I said I hadn’t been dating anyone currently and have just been focusing on work and I’m happy where I’m at. She immediately asked if I am into dudes… I am a straight female and just feel it is rude to question someone’s sexuality just because they aren’t actively dating. What do you think?