I can totally understand your feelings of discomfort regarding this situation. It sounds like you and your husband are honest and clear with each other and it seems you are afraid of his reaction to you feeling insecure about his reconnecting to this lady.
Reader, you have every right to question this new situation as it involves an ex-partner your husband was in love with. You and your husband made a promise to maintain honest and open communication from the start of your marriage and that is exactly what is needed now.
You need to tell him how you feel, and he needs to understand why you feel this way.
It is very normal to have difficulty with a spouse reconnecting with an ex-partner and, in my opinion, your husband needs to question his own reasons for doing so. He must understand you would have difficulties with this, as I’m sure he would have if the shoe were on the other foot. It may be a very innocent and genuine situation, but I would also question her reasons for wanting to reconnect with your husband if she knows he is married with a family.
Either way, you need to speak to him and make it very clear you have issues with him meeting her again. Otherwise, your imagination will tell you all kinds of things are happening and that will hold absolutely no benefit for you or your family.
Be honest with him and expect the same level of honesty from him. I wish you all the very best.