I really enjoyed Carolyn MacCullough's Once a Witch and the sequel (and apparently conclusion) Always a Witch, has a publication date of (around) 1 August 2011 (US).
There's this teeny photo of the cover on NetGalley:
Since the gripping conclusion of ONCE A WITCH, Tamsin Greene has been having nightmares. Though she should be enjoying her new boyfriend, Gabriel, or discovering more about her newfound magical "Talents," she's too busy dealing with her sister, Rowena's bride-zilla wedding demands and worrying about the resurgence of her enemy, Alistair Knight. But most of all, Tamsin is haunted by her grandmother's prophecy that she will soon be forced to make a crucial decision. A choice so terrible, that it could destroy her family forever.
When Tamsin discovers that Alistair successfully went back in time to Victorian Era New York, in order to destroy the Greene family, she's forced to follow him into the past. Stranded all alone in the 19th century, Tamsin soon finds herself disguised as a lady's maid in the terrifying mansion of the evil Knight family, bustling about as a servant, avoiding the watchful eye of the vicious matron, La Spider, and fending off the lascivious advances Liam Knight. As times runs out, Tamsin's brash demeanor and sardonic wit place her in the center of the fray as both families square off in a thrilling display of action and magic. And to her horror, Tamsin finally understands the nature of her fateful choice.