While she has done other things I'm not sure if I would have ever called Carrie Fisher an "A Lister" or even really a "B lister" especially after the third movie. Sure, she worked consistantly, but she didn't have a career like Harrison Ford who was the real "break out" from those movies.
Right now when she's pretty old, and has only that one thing (Star Wars) as a major legacy despite numerous attempts, I'd immediatly guess that she's fishing for attention (haha I made a pun!) more than her having any kind of serious anti-drug message.
1985 aside, I'm almost tempted to say "prove it" since this strikes me as being an "any publicity is good publicity" type of move. But I'm a big enough fan simply due to those movies where in the end I don't csre much and true or not, I hope the attention makes her happy.
Also she looked good in the metal bikini which is in part why it's so famous, I don't think anyone who looked like that in it would need to be high, just receptive to the idea of wearing sexy costumes for a few scenes.
Now on the other hand if she DIDN'T look good in it/the scene, and the whole thing was gross and being done for laughs (like having some 300lb woman coming out for ridicule purposes) then I might see the need for drugs before sticking onself out like that in many cases (exceptions being career comedians and the like who make a living off of physical humor).