Forum:Ashley's Citadel date

What's the latest point you can do Ashley's "date" on the Citadel? The reason I'm asking is because my main MShep is in a relationship with Miranda. If I went to the Citadel to meet with the Asari councilor, met with Miranda at her apartment and denied her access to the Alliance resources (under the reasoning that the Alliance can't afford to part with any) causing her to die on Sanctuary and skipped Ashley's "date" at that time, would I be able to return to the Citadel post-Sanctuary and have the date with Ashley and "lock-in" with her then? Or would it be too late?