The warrior killed by Grendel's mother is Aeschere.
1. Aeschere was a trusted advisor and a close friend of King Hrothgar.
2. Grendel's mother seeks revenge for her son's death at the hands of Beowulf, so she attacks and kills Aeschere to avenge Grendel.
3. Aeschere's death is a significant event in the epic poem "Beowulf," as it intensifies the conflict between Beowulf and the monsters he faces.
Therefore, the correct answer to the question is Aeschere.
