Tell her “Your boyfriend or husband must be very proud of you”

Give compliment to a girl at the very early beginning. Either her demeanour, character, intelligence, caring, ethics, funniness, taste of fashion, make up, whatever

The purpose 1. She cannot use “I have a boyfriend” rejection 2. Know her status 3. Give her an illusion that you just want to make friends

Keep in mind that she is in a relationship doesn’t mean anything.

It plants a seed in the future (in next few minutes, or next day) when you ask her out, for a coffee, a supper or a drink. You “just want a company”. You don’t need an excuse or bullshit to tell her “hey, don’t think too much” anymore. She’ll defuse that for you mentally.