New2grammar1. Can I change 'when' to 'that' as suggested by you before the context was given?
2. Can I change to past tense "She felt..." since the time shift has occurred, there's no need to shift in time again.
1. Yes, but then you should probably change
so to
very because
so ... sets up reader expectation for another clause beginning with
that ...She had been very happy that Dahu chose her.
She had been so happy that Dahu chose her ------ that she jumped up and kissed him. (Ignore the first that. It's not part of the so ... that ... structure.)
Compare:
He was so tall that he had to stoop to enter the room.
2. There's no need to shift again; that's true, although this is a matter of opinion. Most authors will keep reminding the reader of the intended position in time with an occasional past perfect. Theoretically, even those subordinate clauses would be in the past perfect, because they happened during the same time period as the main clauses, thus:
She had been so happy when Dahu had chosen her
as the future mother of his children. He was the best toolmaker in the
group and it was a great honour to be chosen. She had felt so proud as the group had shouted loudly to applaud his choice.
Writers tread a fine line between overusing and underusing the past perfect. Typically, they try to use it as little as possible, but not so little that it confuses the reader about the order of events in time. These are matters of style more than of grammar.
CJ