A lot more of Erynn's backstory with the MC is addressed outside the flashback than in it. For Lexi, all we get to see are the flashbacks for any hint at her backstory.IIRC (been a while)...other than the flashback...neither do we see any relevent backstory regarding Erynn and the MC either....other than that event...
So they are weighted far heavier for Lexi than Erynn. Have to do more with a lot less.