Shaila will usually respond to questions about concentration and jhāna during any retreat, but she only teaches the specifics of jhāna practice at retreats that are described and advertised to include jhāna instructions.
It is understood that meditators may, at various times in their meditation history, experience absorptive states, even without intentionally doing jhāna practice. Although this can indicate a personal aptitude for concentration, periodically slipping into secluded states of absorption or jhāna-like states is not the kind of concentration that Shaila teaches. She takes a thorough approach to the development of the mind that emphasizes the development of mental skills, not altered states or esoteric experiences.
Even if a meditator has practiced jhāna with other teachers, in other systems, or naturally slips into jhāna-like states, Shaila cannot teach the subtle nuances that master jhāna and apply it to liberating insight during her general insight meditation retreats. The jhāna training usually requires systematic instruction and individual guidance, neither of which are available on general insight retreats.