“If they are a big client and they get insulted, then it is YOUR problem.”
No, it’s not – it’s their problem, not LB’s. She did the right thing; they did the wrong thing. They are the ones who will lost out; she will only gain.
Hashem doesn’t punish people for doing the right thing, so she has nothing to lose by doing the right thing. Nothing bad can happen to you as a result of doing the right thing. If a client ends up being lost, either it would have happened anyhow or it will really turn out to be good for her, but nothing bad can possibly happen as a result of doing a Mitzvah.
Someone once came to Rav Shach very upset because someone unfairly took a job that was meant for his daughter (I don’t remember the details, but apparently the other girl had done something that was assur in order to get the job).
Rav Shach said, “You have nothing to be upset about. Your daughter was obviously not meant to have the job. Everything is from Hashem, and the other girl couldn’t have caused this to happen. On the other hand, the other girl is really stupid, because she gained nothing but an aveira, because you can’t get something that Hashem didn’t want you to have”.