I think your suspicions may be right op, she's seeing if you're with him.
Some women do this, I had it years ago, the bosses wife, who were both about thirty years older than me, felt he was having an affair, which I only found out after.
She turned up at the office one day and proceeded to spend the whole time at my desk literally sat next to me, pulled a chair up, and stayed there till lunch time from nine am. Her husband walked into my office, and said oh you're here, and walked out. He didn't come back in.
She stayed over three hours, sitting side by side with me. Eyeing me up and down, making sickly sweet polite small talk, telling me about her great marriage asking me all about myself. It was awful. And weird as fuck.
I was polite back and kept looking at the woman I shared an office with in embarrassment and discomfort. I couldn't work out why she was sitting at my desk like that. Spouses didn't come to the office. As per any normal office.
The thing is, she was right, he was having an affair. It just wasn't with me. It was with another woman at work. I wouldn't have touched him with hers never mind my own.
She'd got it completely wrong. It was just I was rhe new girl who started at the same time as the affair started. It was a small office. So she'd jumped to the very wrong conclusion. She was early fifties, I was early twenties. The woman he was shagging was closer to their age.
It's odd what some women will do. This woman decided making her presence felt was important, like a warning shot. Yours isn likely doing the same, she wants you to see her. She will soon try to befriend you.
She thinks you're the ow.