This ambiguity is reflected in Clytamnestra's words. In welcoming Orestes, she says that he and Pylades will be attended to in a manner that befits the house. On this surface, this means that the travelers will receive a royal welcome. However, as we know that the house sits under a bloody curse, we should be suspicious of any welcome that "befits" it. Moreover, Clytamnestra's reference to "warm baths" is dubious, as we remember that she murdered Agamemnon in his own bath. Perhaps she does recognize Orestes after all, and is trying to lure him into the house where she can do away with him.
More likely, however, Clytamnestra is totally unaware of the danger that strands before her, and speaks words whose meanings even she does not fully understand. This is a common tactic in tragedy and is called a 'double hermeneutic.' Aeschylus uses the characters to convey an ironic meaning to the audience, without making the characters themselves aware of what message they are carrying.
At every stage in Clytamnestra's speeches, we can either read her sympathetically or not, for Aeschylus has left her true emotions in an ambiguous state. Just because she has been cruel and devious in the past does not mean that she could not lament the death of her son. We must remember that it was for the love of her murdered daughter that Clytamnestra killed Agamemnon in the first place.