Tereca is schizophrenic. This is fact. Everyone who knows her or of her is aware.
At the slightest action, whether real or imagined, she can go off on a shrieking fit.
She is loud, insulting, going on and on.
Ann was warned of this by Ms Summers.
Ms Summers is a respectable, well liked woman with friends and family.
Because Ann hates herself, hates the fact she is alone, childless and very unlikely to ever be married and have children, she resents Ms Summers.
To ‘fix’ Ms Summers, Ann befriends Tereca. She makes a great show, (for Ms Summers benefit) of going off with Tereca.
This is because Ann has her own mental issues and identifies with Tereca.