Begging a friend, "Is he the only thrill for me?"

Girlfriend is 39 years old. She has never been married since the divorce. In June this year, I met a man through her girlfriend (the girlfriend met this man through WeChat). The other party vowed that she wanted to get married and start a family, but because she didn't know much about it, her girlfriend was afraid of being cheated, so she wanted to predict whether this man was the only thrill for her or the one she was destined to marry. Please give some advice from friends and experts. Thank you very much