This year has been a busy one for Joan Semmel. She had a solo exhibition at the Bronx Museum of the Arts in the spring, solo shows at both Alexander Gray Associates, her New York dealer, and Art Basel, exhibited at Frieze New York, and now has two paintings at the Paula Modersohn-Becker Museum in Bremen, Germany, in the group exhibition “Sie. Selbst. Nackt.” The title, which translates as “She. Herself. Naked,” could be applied to much of Ms. Semmel’s career as a painter.