Marjorie Bontempo was a changed woman after moving into Life Care Center of Nashoba Valley, a Littleton nursing home where the staff doesn’t believe in using antipsychotic drugs simply to calm residents. A physician had prescribed an antipsychotic for Bontempo a year earlier, after Alzheimer’s disease had transformed her from an accomplished seamstress and demure family peacekeeper into a cantankerous, confused woman who refused to eat.