Tammy Sytch Tried Saving Chyna Right Before Her Death

WWE legend Tammy Sytch says she has "tremendous guilt feelings" about the death of her good friend, Chyna ... admitting she failed to get her the help she needed when she saw Chyna struggling.

Sytch -- aka Sunny -- was on her way to court-ordered rehab this week when she told us Chyna's death has been on her mind for months. The two were very close and would FaceTime every night.

The Hall of Famer says she recognized Chyna was going down a bad path and tried to convince her to go to rehab -- but she refused, and died while Sytch was seeking treatment for herself.

Obviously, Chyna's death isn't Tammy's fault ... but Sytch says she wishes she could've gotten her friend to see the light. Chyna…