There are different reasons someone struggles to discuss a trauma with a therapist.

It can be because of how the person has managed to continue on in spite of what took place, perhaps developed their own ways of interacting in a family without telling a family member abused them in some way too. There is also that fear of sharing something important and not being believed or validated the way the victim needs. It is also not unusual that a victim developed their own unique way of empowerment and ability to be strong that another person will not understand if they expose that part of themselves that was abused/hurt/damaged/a victim, the other person's response might be dismissive or simply not understand how complex that scenario was to the victim and how they managed it the way they did.

For myself, with the T I have now, I had been through so much, had bad therapy and people who refused to believe me and were either angry at me for how badly situations affected me or decided to not believe me and be dismissive, even to the point where I was misdiagnosed. Actually, as my therapist has confirmed, it is not unusual for someone suffering from PTSD to be misdiagnosed as some of the symptoms and how PTSD victims behave can look like they are suffering from other disorders.

The other thing that can take place is if someone experiences a trauma and at the time of the trauma the victim was completely caught off guard in some way, events took place that resulted in outcomes that also came as a surprise too. A trauma victim "after the trauma" begins to realize all the things that led up to the event that they had not noticed and they have the damage figured out, but that had all come afterwards. When they finally get to a point where they can talk about the event, and even discuss the dangers or characteristics in the person who hurt them or caused the events to take place it can be hard for anyone who is listening to understand and believe them with the ability to recognize that what they are hearing is all because of how the victim got to a point where they could put all the pieces together that led to the trauma because of "hindsight" and how they recognized the warning signs that they saw before hand but didn't expect the individual's questionable behavior patterns to lead to the major trauma.

A trauma victim does not want to hear, "If you saw all these things why didn't you", or "do you think that all you are doing is guessing what led up to this and it really was not that way" or even "why didn't you do something earlier?". A trauma victim already really struggles with so much pain and anger that they didn't put the warning signs together soon enough so they could "prevent" the trauma. A trauma victim already suffers a great deal of anger towards self for not seeing the signs early enough. And it is not unusual for the abuser or person at fault to "deny and blame the victim" too. And often a victim faces family members who choose to be dismissive and may want to practice "denial" or even insist the victim is somehow lying for some kind of attention or gain or manipulation or she is "just over reacting so just ignore her".

So when it comes to "trusting" a therapist to not be dismissive or react in any of the ways expressed above, it is often very hard to finally talk about a trauma, or maybe several traumas. Also, depending on the trauma, there can be some things that are blacked out in the memory and a real concern about wanting to know all that took place, yet fearing that remembering it may be too much to bear emotionally or psychologically.

One of the things I recommend doing "first" is to discuss the topic itself and see how a therapist responds to that topic. That is what I did when it came to discussing CSA for example. However, there are different ways of feeling out a therapist with regards to how well they might respond to a trauma by discussing the way these types of trauma's can take place in general. For example, what I have said above? A person can actually talk about how that happens with people when they struggle to talk about a trauma and are at a point where they can look back and identify all the warning signs, yet they didn't recognize how these warning signs were going to produce the trauma until the trauma took place. A good trauma specialist will be able to say that "yes" this is definitely what takes place and is a common challenge with trauma patients.

Hope that helps to give you some ideas in how to slowly come to a point where you can probe and get to a place where you are ready and trust the T enough to finally share a trauma. When I experienced a trauma and
suffered from post traumatic stress, I trusted that professionals would
know how to help me, I was wrong about that. If that does happen, it's not the patient's fault, no one really thinks about trauma and how it
affects people and what post traumatic stress means and how to make
sure you get the right kind of help for it.

(((Hugs)))
OE