Mersea as ever I agree with Kew! Offering to stop going will hopefully be enough to make them realise you do not 'need' it and then they will not mind if you have it! But they may say 'OK stop going then', in which case you will need to decide how much you need this and how long you wish to continue with it before effectively 're-starting' the adoption process.
If I can play devil's advocate - I hate the word devil but love advocat (the drink!) - can I say one interpretation of your attending counselling is that you are having a hard time coping with life at the moment. That your parents' illness and the adoption process is so stressful you need help to get through it.
I am not saying I think this is true!
But from a social worker's point of view if it were true you could not handle your parents illness and the adoption process without ongoing counselling then they may feel you would not handle adoption itself well.
Adoption is generally more stressful and full on than the adoption process (in my experience) although for a very small number of people who find interviews and meetings highly stressful and who adopt relatively easy to care for kids this may not be the case!
In other words once your new child or children arrive you will have more to do, more calls on your time and money, less 'me' time, more stress generally (although also lots of fun, at times, but maybe not at first!). So, if there are any questions about your ability to 'cope' the social workers will want to know about it and want to ensure it is 'sorted' before proceeding.
This seems very unfair on one level, because (for example) I had informal but professional counselling for an eating disorder before we adopted, it stopped when we adopted but the stress of adoption made it temporarily worse (IMHO) so I went back to see the counsellor.
Because this was all though work (kind employers) and nothing to do with medical records it never showed up anywhere. I was open about my (frankly rather mild) eating disorder to social workers and it was never really an issue, possibly because eating a lot (a bit too much) is actually very common! Even my social worker admitted liking chocolate when stressed or the whatever!
So take or leave my view, I am an adopter and not a social worker and I am not saying I agree but it is one interpretation of why they are bothered about this.
Mersea please PM me if you like and please do not be offended!