I've been searching and searching, and I can't find any info. I'd rather not run multiple iterative playthroughs to find out this one detail...
I see a total of four outcomes relating to the dragon:
Convince her to help you attack Eothas and avoid fighting her
Convince her to help you attack Eothas and betray her to Rymrgand (also peaceful)
Fight her, and allow Rymrgand purify the relic
Fight her and don't allow Rymgrand to purify the relic.
All peaceful options do not seem to give you the trinkets Neriscyrias' Hope and Whispers of Neriscyrias.
Does purifying the relic make these items useless or otherwise change their effects?
If you do not allow Rymrgand to purify these items, are you allowed to summon Neriscyrias later, or does she otherwise make an appearance?
Is there any difference in defeating her vs. striking a pact with her, if you don't allow Rymrgand to purify the items?