I think your decision is the right one. When we meet someone in a group, we are both in vulnerable places, and we are working on individual issues within a group. There are also many parts of ourselves we do not bring to the group. Being in a relationship with someone in the group will inevitably draw your focus away from the group and your purpose for being there. Think of it as kind of transference, to a member vs the t/group leader.
If you were to meet this person after the group is done, and in a different circumstance, it might be okay, but they will not be the person you created in your mind during group (whether you are aware of creating this person or not, you do)---
Right now, it is important to focus on the group rather than distracting yourself with lovely romantic fantasies...your post seems to say you already know that.