So something similar happened to me when I was 23 (over 30 years ago). This is all true. The woman in my office was 42, single, divorced, no kids. I was the youngest and only single guy in a 60 person office. I thought the same when she asked me to lunch the first time, same dynamic, she kept touching me, etc. My solution was to immediately ask out the hot 24 year-old accountant, the beautiful Vietnamese 25 year-old payables clerk, and then the blonde 25 year-old amply-chest-endowed assistant to the CFO in quick succession. In six months I had slept with 10 percent of the women in the office. The older woman got the message.
So try that.
Unfortunately this blissful period for me — the best and only successful period of my career as a Romeo — being the only fish in a desperate pond got all screwed up when I reconnected with my later-to-be wife, who didn’t work at the office.