A big sister in our unit was very kind to me and suddenly ignored me. ....

I also think this sister must have heard what others said, and someone in the gossip must have maliciously provoked the relationship between you two! Imagine that the relationship is not bad at ordinary times, and suddenly one day you are late and she ignores you. It must have happened between the night before and the night you entered the office, and it is very likely that this elder sister was angered and had a great prejudice against you!

Generally speaking, it is normal for employees to be late. She is only a member, not a leader, so she can never ignore you because you are late. I think more than 90% people speak ill of you in front of her!

From your talk, I can see that you care about this big sister very much. She has a good impression on you from the beginning. Imagine that your age is 10, and she is very enthusiastic about you when she first came to the company. I can see that she was friendly at first. As for what happened at her place, I suggest you take the time to ask her out for dinner, ease your relationship, and find out what's going on there and who is holding her back. !