Can you send your counsellor a letter to say thank you/how you are doing?

[English]

I think it would be ok if it was an email or letter. If you reference anything you considered private in therapy you are thanking her for then a letter would be better. Sending an e mail is ok, but many emails are read by someone other than person it is stickly intended for. In fact, many people make fun of their 'stalker bosses/HR people because software companies make programs made to monitor emails to keep down theft of private info and defend against other problems.
If you chose snail mail avoid cards because many people see cards as gifts. I think giving therapist and prior therapist gifts is frowned on. But I think letting her know you appreciate her is a great idea. I would have trouble finding a problem with saying thankyou!