I had a TOTALLY different view of Catherine's tears.
I think that in spite of how far she's come after her childhood problems, she doesn't have the highest self-esteem in the world. She thought that Leslie was awesome and genuinely LIKED her. I think that C thought that L would be the best choice for Sean, and when he sent her home, it shook her self confidence even more. She'd spent a day watching Desiree (I think that's who it was) throw herself all over Sean while she and the other girl commiserated with each other about feeling like the two of them were on a Sean-and-Des date. Then he sent home her friend, "the best choice for Sean." She said she doesn't know what's going on and she doesn't know where his mind is now. I don't think it had crossed her mind at the point where she was crying that Sean might actually have preferred her to Leslie. Part low self esteem, part genuine humility.
JMO. I could be wrong. I was once before in my life. Wait . . . oh no . . . I wasn't! ;-)