I know sikret has delayed Nalia's complaining in consideration for lower level parties, but currently I feel I'm still too low a level to take on de'arnise keep. So I would like to know how many times will nalia complain before she leaves forcibly? TIA

Twice.

Her first complaint is delayed for 4 (more) days in IA:

In the vanilla game, she would complain 3 days after joining; now she will do after 7 days.

The time between her first and second complaints is not changed.

So whats the time between her first and 2nd complaint? Thanks

Three days and then she will leave. You should go to the keep before the second complaint actually kicks in.