When Sevar and Subirachs show to see if Sevar's soul is salable, the Grand High Priestess of Asmodeus is also there.
There are many reasons for this, but mainly, because it is now also her duty to deal with 'tropes', as it is her duty to deal with 'gods'. The degree to which Keltham has guessed that something might go wrong with this sale, which is far more probable than Keltham has any just reason to believe, is sufficient for Aspexia to consider what it is she must now do if a 'trope' is controlling this situation fully.
And if clarification from Hell is forthcoming, let her perhaps be present to hear it in person and even ask a question or two.