Credit: Arnold Turner/PictureGroup via AP IMAGES.

Prior to Whitney Houston's death, her sister-in-law believed that drugs would likely kill the singer one day.

Oprah Winfrey's cable network, OWN, has released a preview clip of her interview with Whitney's sister-in-law and manager, Patricia Houston, that airs Sunday. When Winfrey asked her if she thought "drugs would end up taking" the iconic singer, Houston replied, "The handwriting was kind of on the wall. I would be kidding myself to say otherwise."

Winfrey then asked Houston if she was afraid that Whitney would be gone too soon. Houston answered, "If things hadn't changed. But things had, were, changing. Things were really changing with her. Very much so. It wasn't about substance abuse or anything like that….I was afraid for other things, lifestyle, more so."

Houston added that Whitney was looking for love in all the wrong places.

Oprah's interview with Houston, the singer's 19-year-old daughter, Bobbi Kristina, and Whitney's brother, Gary Houston, airs on Oprah's Next Chapter this Sunday at 9:00 p.m. ET.