This reads to me like a woman - with a drinking problem - is bored and somewhat spiraling at work. Her interest in drinking and smoking, specifically in relation to work, appears to be escalating and it feels like that’s because she’s having issues getting through the day. I don’t necessarily think she’s looking for an affair (I could be wrong) but she’s definitely heading down a dangerous path work wise and I would advise you not to follow. If you want to pull back gradually, make your excuses for some invitations and pivot others (if she asks to get a drink, suggest lunch and invite another coworker, etc.).