In addtion to being the hero of the Sol Zone Blaze also was also born into the role of Guardian of the Sol Emeralds, naturally Isis would have been trained to eventually assume these responsibilities at an early age making her an excellent counter to Lara-Su. Both characters are actually fairly similar, both have inherited a great responsibility, both had the benefit of being mentored by their parents, and both have allies that they can call upon to assist them. You would think that being so similar they would get along great! Not quite. As similar as she might be to Lara-Su Isis differs from her in a number of ways, oh sure they can get along and work together just fine when the need arises but for the most part their relationship is more akin to how Sonic and Knuckles treated each other in the beginning.

art by  Ebonychimera
Isis © me
Lara-Su © archie comics