I def thnk the ABA group would be good for you and your DD and it seems your leanng that way, maybe say to the ladies you've found a group with kids your D's age but you would love if you can maybe still come once a month for a catch up or organise a play date once a month with them and that you would like to keep in touch.
Maybe you could print out a 'thank you' card with a pic of your DD (do it through Big W or something and use the 15c prints ) and say thank you for being a part of our life, we hope to keep n touch and have your details on there. ????