They do, but in her case the drug was apparently alcohol (everything I read only referenced alcohol, DUIs, domestic abuse calls, and a tragic downward spiral following a miscarriage in 2003). That said, alcohol is rarely the only drug chosen by someone who abuses substances to this extent. It is also why she left the show and was replaced by another actress, reportedly. Not to make too light of it, but anyone who goes by either one or three names probably has identity issues, especially if its three first names. I can't think of anyone famous that goes by three names that isn't just a little bit off.
It's very sad. She was a real cutie, and I always liked it when she was on screen. Pity. Those of us who are not susceptible to being influenced by drugs, including many legal ones, are exceptionally lucky.
But even the most benign drug, marijuana, can ruin the trajectory of your life by robbing you of personal growth and initiative. Don't let that happen. Being around other musicians I still only used it mostly off and on and even then only on weekends, and just a little bit, recreationally, but for 27 years; 18 years later I am still trying to recover from not doing all the things I should have done but did not do because of just being stoned. Regret also sucks.