I'm not a fan of the Summer's death theory either, I think there's a subtle hint in the story that Nami was involved in her disappearance. I think cheeto beauty feels guilty about it, so she won't repeat her mistake and interfere in the MC relationship with Bella.
As for Summer's disappearance, I think she'll show up somewhere around chapter 8, right around the time when the MC gets his personal life together and becomes his old self. Summer's appearance will make our hero completely lose his mind
Mission Accomplished.
When it comes to Summer we don't know much about her. There are a lot or orphans in Summer's Gone, including the MC, Nami, Victoria and Maja, all of who lost their parents while very young. Could Summer be in the same boat? Maybe another orphan who had been adopted, fostered or was living in care and supported by social services? If Summer did have a family did they vanish when she did? And if not who are they, where are they, and what have they been doing? (Could Summer be a member of the Frohn or Zane clans?) Summer can't have been much older than mid-teens when she vanished, which would have made it very difficult for her to have run away and stayed gone without significant help from someone, or some people, significantly older.
(Not completely impossible for a teen to vanish but without assistance, money and resources very hard to pull off alone.)
Until we know more about Summer's backstory and the shocking events surrounding her disappearance, which traumatised the MC and rendered him partially amnesiac apparently, all we can do is to speculate about her fate. Nobody in the story so far, including the MC himself and Nami, have ever said anything or behaved as if Summer has perished and actually known to be deceased. Personally I firmly believe that the Summer character is alive and eventually will reappear at some point and convulse the life of the MC for good or ill. I find it hard to believe that a character who has lent her name to the title of the story, whose disappearance is directly responsible for the MC's suffering and plight, is going to turn out to have died five years before the story began without anybody knowing.
(That just doesn't seem right to me at all.)
I've been looking at WiaB and SG when I have the chance and kind of think that they really may be set decades apart. In WiaB the male hairstyles (pony tails and mullets) and designer stubble plus male/female fashions have an 1980s "Miami Vice" vibe about them, whereas SG seems much more contemporary and suspect that the stories could be as much as thirty, forty or more years apart. It could be that events occurring in WiaB have echoed down the decades causing, directly or indirectly, several major events in SG, possibly even having a hand in Summer's disappearance itself.
Can't really sensibly even guess at what's going on with so little information available at this stage in the game.
