Parenting seems to generate a form of PTSD, no matter the age of your child(ren)!
I also have a 30+ daughter who's a life-long risk-taker -- she climbs mountains and goes cycling through South America on her own, for example. I've also focused on letting her live her own life, no matter what "holes" she gets into. This is not always easy even when she makes generally good decisions. As her mom, I want to be supportive and helpful, to protect her from harm, and to make her life easier. But it is not in our job description as parents to fix our children's messes, especially when they're chronological adults.
The shame and guilt you may be feeling is normal. But know that you are always doing your best, and so is your daughter (even when she falls in a hole). On her life-path (at the spiritual level at least), making poor decisions and digging holes for herself now may be necessary so that she can learn how to climb out of them. By not tossing her ropes or building ladders for her, you're silently allowing her to build them for herself.
This is what life is about -- learning to take care of ourselves (even if we also help others). Most children don't want their parents meddling in their problems, no matter how bad it gets. Pat yourself on the back for letting her live her own life instead of beating yourself up, as best you can.
As for the PTSD, it's normal, maybe inevitable, and part of the job. Decrease your "trauma" by doing whatever can bring to stay centered when your daughter's dramas throw you off balance. Trust that your daughter will (or does) appreciate that you're a supportive parent and a good role model rather than a "smothering mother." I hope this can help you shed any feelings of guilt and shame.
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