They could be from just being handled/recovered. Pulling a wet corpse from a river doesn't sound like it could possibly ever hope to be a very "gentle" event.
And some of the redness could be from temperature or moisture changes. The morgue or even the riverbank (wherever pic was taken) probably wasn't all warm and cozy, but I'm sure it was much warmer and a whole lot drier than that river is in December. Maybe she got snagged on something while floating down the river and got damaged that way.
I wonder if salinity, like "backwash" from the ocean (I know the river isn't really swift or super powerful there) or pollutants could've affected her in any way. It's not too far from where the river gets fat and becomes Delaware Bay (basically an inland extension of the Atlantic) so it has to be a lot saltier than any of the creeks and rivers where I live.
I actually think the Ohio River in Louisville is really pretty gross. And it's only been through three "kinda/sorta" big towns by that point (Pittsburgh, Cincinnati, Louisville) but plenty of farmland with manure that's not just made by animals but saved and spread all around as fertilizer. I've been around the Delaware River a little bit in my lifetime. My mom did her residency (or some doctor-making thing) in Wilmington and still has some friends up there so we'd go up there every few years. I didn't study it or even really do that much around the river, but I got a good enough look at it to know that I definitely wouldn't ever want to touch it. I couldn't even imagine swimming in it. City junk that gets in rivers up there up there is probably just as nasty as the cow manure tea that's my local gross-river-making thing. Just in a different "really, really gross" kind of way (used needles, dead mobsters, Three Mile Island slime, etc).