Yes, whatnot, follow your instincts, because they're rarely wrong. Perhaps putting a quizzical and unwelcoming expression on your face the next time she floats in, or is found to be visiting again, may just do the trick.
Reminds me of years ago when DH worked at a pub in the evenings. I was in my early 20's then, and quite fiery
. I'd noticed that this dainty wee barmaid (I have never been dainty or wee) was doing quite a bit of flirting with him and when one of the customers 'light-heartedly' commented that 'M' seemed to have a fancy for DH, I took matters into my own hands. That evening, we visited the chippy after he'd finished working, and who should be there in the queue but 'M'....
. I sidled up to her, and gave her a very sharp kick in the ankle. No-one noticed anything except her. Now, of course, I would never do anything like that nowadays - and wouldn't ever advocate violence....but it did work 45 years ago.....no more problems. 