Whenever John is out, Sherlock needs someones help for his 'experiments'

It's a hot summer day, and Frankie didn't have any AC, so she goes to the window that faces the back yard of 221 Baker Street, and Sherlock sees her through the open window. He asks what she was doing in there and who she was, and after stating that she lives there he insists that it's always been empty he vanishes and reappears at her door. He barges in, snoops about and gets irritated that he didn't notice. She kinda does an awkward introduction and offers tea when he rushes back up to his flat, requesting white tea, two sugars. She brings it up to him with shaky hands (due to mental/emotional things), so the tea sloshes onto her hand and burns her. She winces, but bears with it as Sherlock watches her from the top of the stairs, impressed and says, "You'll do. Come in."

After she walks in and addresses the smiley face decorated with bullet holes in the wall, he presses a severed foot into her hand. Frankie isn't shocked, instead mildly amused and says, "Oh, a severed foot. I've always wanted one of these, thank you so much." and that once again impresses him. He says, "You aren't easily shocked are you." I can't remember what she said in response, unfortunately. Then Sherlock deducts that Frankie was Mrs. Hudsons great niece, but is corrected; she is her grand daughter. He gets slightly annoyed by this, but she continues to examine the foot closely.