Adultery v Unreasonable Behaviour

Is it unobjectionable for a petitioner whose only ground of complaint against the respondent is an adulterous relationship to rely on unreasonable behaviour instead of adultery in her petition?

It is unobjectionable. However, there would seem to be no point unless the petitioner's case was that she did not find it intolerable to live with the respondent but that it was objectively unreasonable for her to be expected to live with him: a fine distinction. In neither event is there a requirement for the person with whom adultery is alleged to be named.