Sure, I am not a native speaker. But you don´t get it culturally.
The Milonga is not a zoo were you go to spy people dancing, I don´t like that. Specially when there are intruders in very traditional milongas, they only disturb milongueros and dancers because they don´t understand the social way to behave there. The walk through the dance floor meanwhile we are dancing, they sit with a chair on the dance floor or with a leg on the dance floor or the chat standing on the dance floor avoiding us to cabecear.
I suggest you take your mother to take some tango lessons, that would a way to make her participate of what Tango really is, on the other hand, it might change her life.
Maldita milonga is a good place for that, she can dance a little after the class and se the orchesta live and some people dancing. On the other hand, this place is full of people who has no idea about tango or milonga codes, so she will feel comfortable without disturbing anybody.
Regards