On a boat, anything is repairable. The question is whether it is worth fixing. That depends upon you and how much you want to spend in time or money to fix it. Joshua Slocum got a really decrepit, old and worn-out fishing boat, fixed it up, and sailed around the world. Our cabin top had 2 delaminated sections about 1' x 10' where the handrails had leaked, rotting the balsa core. We fixed it. Our hull had a 2' diameter "spongy patch" below the waterline on the aft starboard quarter: I fixed it. There'll be more to do next spring somewhere else, but we think we can keep ahead of it (and perhaps work to prevent some of it too.) Fixing things in your case are made tricky by the inside liner. ", You may be able to take all or part of it out to access the area, or you may have to work from the outside. If your core is rotted, it will need to be replaced. If it's simply "unstuck", you'll need to goop it up (epoxy sticks better, but using polyester resin may help avoid hard spots that could cause problems later) and figure out a way to press everything together until the glue kicks off.
Read a few books and talk to several people who repair boats to get an idea of what is involved. You may decide it's time for a different boat, or you may decide she's worth fixing. Your choice!