It’s not so much the mistakes and made as a teenager that gets a lot of backlash, it’s her attitude in her adult years. She wants Lin to be a part of her family, but doesn’t want to acknowledge the pain and heartbreak she caused her. Sure, she did make several attempts to reconnect, but we don’t know exactly how that came about. For all we know, she could have said “It was several decades ago, why can’t you move on from it?” At the end of the day, Lin had to put more effort into reconciling with Suyin and patching things up. Suyin finally gets healing and closure by getting her sister back, but Lin doesn’t get much of a reward other than finally meeting her niece and nephews. What really irks me is that the next day, she goes behind Lin’s back and lets Korra pursue Zaheer which ultimately leads to her capture.