Dear Natalie,
Welcome and thank you for helping your mother with computer skills (I really need my daughter to help me and this mother thanks all the daughters).
The good news is that they caught the spot early. They started your mother on a bisphosphonate which helps in a few ways. It strengthens bone so they will not fracture easily, they circle the cancer spot and 'wall' it off, and the other thing they are studying in trials right now is bisphosphonate being able to prevent further spread.
I do not know what chemotherapy your mom had before - but triple negative responds very well to chemotherapy.
Please know if you have any questions there are many wonderful sources of information from the people on the forum and in the resource section.
Not that any place is good to have another location of the tumor showing up - but if I had to pick...I would pick bone before organs and she may find the bisphosphonate works really well for her.
Love,
Connie