Congrats on your PhD.
First of all, why is that you want to reconnect with her? Is it to put the past behind you and start afresh, or is it because you think that reconnecting with her will finally make her admit what happened, apologise and leave her husband? Because I suspect that if that's what you want, you will be disappointed and hurt all over again. I think if you decide to reconnect with her, you must think very, very carefully about what you want from that and how you might feel if you don't get it.
If you have accepted that you will never get any admission and apology from her, and you can cope with being in contact with someone who still lives with the man who abused you (and I don't think I could, in your situation) then by all means get in touch with her. But if your hope is that something will change in her attitude, then I think you are opening yourself up, potentially, to be hurt all over again.
If you do want to reconnect with her, I also think that a formal, very public occasion - meant to be a celebration of your incredible achievement - is not the best time and place to do that. You deserve to have your day in the spotlight without it being overshadowed by the additional stress and worry of having someone there that you have very negative associations with and whose company might bring back a whole lot of difficult and upsetting emotions.
If you want to get in touch with her, maybe something a lot more low-key. Perhaps you could send her a graduation photo and a brief note afterwards and see what happens? But do take care of yourself and proceed with caution.