Thank you all so much for your replies and ideas. Here is an update on the situation: After great advice here, I created a detailed Potty Training document outlining the steps that I will use once potty training has begun. I clearly outlined that in order for the child to wear underpants only, I have to have seen that they are able to let me know when they need to go potty, are able to pull up/down their clothes themselves and are able to be accident free for 5 consecutive days. The DCG in question meets none of the criteria so I gave the DCM the option of sending the child with pull-ups, those heavy waffle cotton training pants or a pull-up over her underpants. I have initiated conversation three times now (once in person, once by email and once by text message) and all three have gone unanswered. DCG was dropped off again this morning in underpants only (the DCM now practically shoves her through the door and runs off before I have a chance to speak with her or check DCG for pull-ups). I really don't understand why this has become such an issue. I don't know what else to do. I have delivered a clear Potty Training document to all parents, I have initiated discussion several times and I have explained my position. I was thinking of sending an "official" letter to DCM today with the following points: "I have addressed this several times now... DCG cannot wear underpants only at the daycare... she is not ready and starting tomorrow will have to be dropped off wearing either pull-ups or training pants or she will not be allowed to stay... I have attempted to initiate discussion and it has gone ignored... if my daycare rules continue to be disregarded, I will not be able to continue care of DCG.
I'm just really having a hard time understanding why they are so unwilling to even entertain my rules or open a discussion with me - I guess it's because I've only been running my daycare for a year and haven't encountered this before. This DCG has been with me for the whole time, but I guess there have been signs... disregarding other minor rules, showing up late for pick up on several occasions and referring to me as the "babysitter". Ugh.
Thank you all for your support. I thought I was crazy until I found this forum. It's my daycare lifeline.