HRT information

Evening all,
Just looking for a bit of advice. I’m slightly worried about a family member
They have been taking HRT and have started to notice a bit of bleeding. They have gone straight to the doctors and had things checked, cervix, ovaries and tubes all fine.
They went to do a biopsy I believe but it was too painful so they have to go back and general I believe to have a look what’s going on.

They said if they aren’t happy with something they will remove stuff.

They have measured the lining of the womb and it’s measuring 2mm.

Can anyone help explain this to me.

Thank you and best wishes