As Jess has pointed out, the only definition of a 'good' therapist is one who makes you feel comfortable. She should spend the first session gaining your trust and taking an overview of your life so far.
I hope the word 'forgiveness' in that link I gave you didn't put you off looking at Pete Walker's site, because he warns against what he calls premature forgiveness and makes it clear that some familial abuses are unforgivable.
An extract from another page of his:
"The genesis of complex PTSD is most often associated with extended periods of ongoing physical and/or sexual abuse in childhood. My observations however convince me that ongoing extremes of verbal and/or emotional abuse also cause it. Moreover as an upcoming article on my website will explicate, long-term childhood emotional neglect alone can also create complex PTSD and a propensity to emotional flashbacks."
~ http://pete-walker.com/fAQsComplexPTSD.html#complexPTSD
Pete specialises in Complex PTSD which, in case you haven't heard of it, bears a close resemblance to PTSD-simple or combat fatigue. C-PTSD comes about through interpersonal trauma whereas PTSD-simple involves a life-threatening event or natural disaster. C-PTSD's toughest feature is that it affects people relationally, as you expressed in your first post.
I hope you'll be lucky with the therapist you've booked to see. If she says anything that feels off to you, I hope you'll screw up your courage and say so. She might be able to reassure you. If not, and certainly if she seems offended, you'll know this is one to strike off your list. In that case you'll need to ask her to refer you to someone else. There's no point trying to have relational therapy with someone who's not up to the job.
When you made the appointment, did the person ask for a brief summary of your problem?