You also said you know nothing of her so you are jumping to conclusions about her motives.
Have you thought it could be something else entirely? Maybe she works in care (many young migrants do), encounters lonely older people in her day job and sees it as her mission to talk to older people who are alone at the gym. You said “she pushes herself onto the oldest female” so, by the sounds of it, she’s not only talking to you.
Why not engage her in a conversation just the once and find out a bit more. It could be that she has no family in this country, is looking for a mother or grandmother figure.
There could be any number of reasons why she wants to talk to you. Fair enough, you want to do your workouts without interruption but it doesn’t hurt to be civil - but also be firm if, having spoken to her, you feel she is wanting some social connection that you are unwilling to give.