P, this is just my POV on R others have with my children. For example, I don't care much for my SIL, but I see how she cares for my kids and I don't keep them from having a close R. I don't see my kids and I as a package that way.
I wouldn't return the gift. I don't see harm in it. I feel it's keeping your D from receiving deserved acknowledgement of her special day. Maybe there's pettiness in how it was given to her, but it did get into the right hands for getting it to her. She's being awkward, but she's still thinking of your D. Maybe she's coming a little out of the fog and truly missing D. Personally, if a person means no harm and is giving love and attention to my kids, I wouldn't interfere in their R to that person. The more people that love my kids the better.
I think it was a brave gesture. Like you said, you might be seeing the old version of W. She could be testing the waters with D as she wouldn't be as rejecting of her. She did make the attempt to give D a bday gift. Why would she even bother if she didn't care? She could have not done it like the Xmas gift.
Don't know if this is advice, but just my opinion fwiw. I do say that I get won over if someone is great with my kids... hmm...?
Hope D has a great day!!
M40, H39 M17 T20 D13, S12 H moved out 05/09 D filed 1/10