'Is this what happened to me and Ferdinand in my previous life? We both assumed things about each other and those who knew otherwise never tried to correct it?'
If so, then all the more reason for Arabella to let Ferdinand know what truly happened with the river nymph Ara.
But she could not tell him the name and appearance either since once she informs him, he would figure out that Ara may have been Arabella in the past life. And once he knows it could have been her, he would likely feel several times more guilty about what he did back then.
Arabella didn't want to make him feel too terrible about it. She only wanted him to know that the river nymph he lived with, loved him and waited for his return. Somehow, she felt that the anger and frustration she was feeling would subside once she did so.
"She only realized that her hints and feelings did not reach you when you told her you were to go back home. Do you recall the time she hugged you when you said you would leave soon?"