Honestly is the very best policy...I wish you the best in your years to come. I may not be present for all of your firsts but I sincerely hope that in time I can see many more to come...My love is with you even when I may not....My heart is full of pride for you and the beautiful woman you are becoming and I certainly miss your happy smile every day...
Warm, honest thoughts are what should be in a card of celebration...definitely upbeat and no guilt or negativity..(not saying at all that you would, just mentioning)...
Life is hard for children of divorce, then add a new woman in the life and then another child. My children live with me but I know that they think "the baby" our child together with my current husband is spoiled....well, guess what, so are they..haha! They just don't see it...like many children, (and adults) their view point is personal and perception can be fuzzy to say the least..if her mother is not supportive and positive to the changing and growing circumstance of the other household I can see where the daughter would just sink deeper into feeling less than in your household. Once again, I am not saying this is what is going on, I am merely saying it is a possibility.
I wish you the best of luck. I am uncertain as to whether you maybe should send her a greeting as well but for some reason I feel like it might be a nice gesture to show your love and support as well.