This hits home so deeply I can't even express it. My birth daughter was conceived by rape as well. I hate to use the word but I despised her while carrying her. It was not until I saw her little helpless being that I melted and my love that I have for her has become what it is today. I NEVER wanted a closed adoption though...I wanted the option of her knowing who I was and me knowing who she is. Our story is the perfect story of a violent conception adoption IMO.
Honestly, there isn't anything you can or should do to encourage her to want to hold the baby or see baby afterwards. You have to give her the space for her to see what she needs. For some it is a closed door after the birth, for some it is a lifelong relationship of some sort. She is the birth mom and honestly, this is one choice that
is hers. For you to leave the door forever open is WONDERFUL and amazing. Please please please leave it open eternally for her and your child to come and go as they please. I really think it helps sooth the soul and heal wounds as they reopen. Even just the knowledge of that being available can be healing. Painful as well, but truly more healing.
I think handing her your number, the number of your lawyer, and a heartfelt letter letting her know the door is always open is all that you can do to let her know that you truly mean she can have open contact. As for a gift, honestly I would have valued most anything. I did not receive a gift at the time. However, my birth daughter's mom sent me GORGEOUS pics when she was about 2 weeks old that are still to this day some of my favorites and make me flash back to that time(in a bittersweet way-I remember the joy for seeing her face again like it happened yesterday

). A necklace or something that can forever symbolize the process will likely be treasured forever, even if she hides it away for the pain.
Please also ask her to reach out for support. That isn't an easy thing for you to do but maybe compile some materials on how to make contact with other birth moms and therapy would be beneficial. One other thing that has recently become a cause of sorts of mine is to try to get doula services for birth moms. I think it would be a powerful message if you guys offer to pay for her to have a doula so she doesn't add birth trauma to the list of traumas.
Please feel free to PM me ANYTIME. I will answer any and all questions!! And sorry it took me so long to see this...this board seems to come and go with people needing it.