I wouldn't sweat this too much. Chinese airlines aren't noted for being proactive, and I think at this point the CA woman gave you your options. They aren't going to address right now, what they feel could be a non-problem. 70 minutes is possible if your first flight is on time and you already have your boarding pass. In the event you don't make the connection, then it's time to put the ball in CA's court and make them find an alternative, which might mean an overnight somewhere but it certainly won't mean being stuck in Beijing until Sunday. There's a 21:10 - 00:35 PEK-KMG flight, overnight there, followed by a morning 11:10 KMG-RGN flight next morning. You'll get to your destination about 13 hours later than planned. Other routings are possible using other Star Alliance airlines via BKK or SIN.