Well, Picard at least had a body Q could reanimate. Janeway's body is gone, turned into starstuff.
More like dissolved into organic goo but yes, Picard was dying on the operating table and would have died if not for Q being so fond of him. Janeway has no such effect on her Q companion and no body or situation for her to alter.
Q can recreate her body with a snap of a finger, or less. Did Q save Picard because he was fond of him? And why did Lady Q bother to save Janeway, if she had no such motivation? The Q don't intervene with human history unless it is necessary.
Actually, they intervene when, where and how they like "for the lulz" it seems. And yes, Q and Picard had a rather unique partnership in TNG, the female Q's actions come off more like pity, allowing her a continued existance without her body, rather than suffer a sudden traumatic death.