You must do whatever you feel is right Jaysus, only you know your so called friends, only you can make that call.
I suggest sending a class email so that you put to bed the rumours, she will never ever expect you to do this by the way - she is counting on your silence and dignity trust me. However if you bring the matter to light gently and carefully you are able to grapple some control of this. You will definitely get replies, and you will definitely have a percentage of parents behind you (it would be zero left to her - I am sure she will do a great job painting you as a harlot stealing her husband, and all she has done is support you through your divorce)
Grey rock works wonderfully with normal functioning women and men that are within the healthy range of rational. It absolutely does not fucking work with deranged psychos. Why do I feel this way? I learnt the hard way. I ignored the rumours, I swanned past every day indifferent, but she planted a seed in every single person's mind, and wove such a web of lies most of my friends didn't know who to believe or what to think.
You have to get your truth our there, whatever way you do it.
I can only tell you that next week is likely to answer all of this, if she does what I suspect she will do, it will leave none of us in any doubt.
Close her down with the truth before she ruins you and dd.
I have had direct experience of this, and I can tell she will not play fair nor does she care about the carnage she will cause. She is playing a kids game in an adults body, clearly with some serious issues.
I hope next week goes well, you have all of us.