My AD has an opiate addiction and the first big sign was being overdrawn at the bank and then subsequent desperate acts to get money. If your D is already losing all her cash to drugs, then things will get worse when she runs out. Expect lies/manipulation/theft to follow.
I pray that your suspicions are wrong but it would not hurt you to educate yourself about addicition- there's a lot of good info on this forum and the web and you might want to look into recovery resources in your area (eg detox/rehab options, support groups for you and your family such as NA/AA/FA).
Please take care of yourself because codependence can be terribly destuctive when an addict is involved.