As someone who has line managed and supervised a lot of therapists in my time, for the love of God do not encourage her to go around saying she's "highly sensitive" or any type of flower child in any interviews or workplaces, either. That will not go down well, because in a work context, managers will read that as "thinks they're a bit special, won't want to do the bits of the job they don't like and will fall to bits if given any feedback that isn't positive". The therapists I've had to manage over the years who labelled themselves "highly sensitive" have also been a pain in the arse as colleagues and employees, I'm afraid.
Being empathetic is only a small part of what you need to be a good therapist, and if a long career in mental health has taught me anything it's that I really REALLY wish people understood it's a lot more than empathy and listening before going into training. You need to be quite a tough cookie to be a successful therapist and not burn out, if you are a sensitive soul.
There is no career in the world that will not have some elements of it that don't play to your strengths, you don't enjoy, or that are difficult. It's the bits you do enjoy and find fulfilment in that make those other less enjoyable or comfortable bits worth it. So, what does your child really enjoy, and does that enjoyment mean she will be quite willing to deal with the parts that are a bit mundane (as a therapist that might be session notes or diary management, for example) or emotionally challenging, again in the context of therapy that might be having difficult conversations with clients, chasing late payments, dealing with non-attendance and dropouts or bad reviews online/feedback to your employer, having to report a safeguarding issue when a client doesn't want you to, etc.