Is MIL from a different country and different ethnicity? believe it or not, yes, some cultures are still a very patriarch society and do not consider the spouses, particularly wives as part of the "family." They are kind of appendages.

You aren't part of the "blood line."
Look at the British Monarchy, for example. If Charles had become king, and was still married to Diana. When he died, succession would go to William, immediately. Diana would be "dethroned" so to speak. They wouldn't wait for her to die, then William steps up.
In some cultures, there is a definite family hierarchy. I know of an Indian family where the family hierarchy went in descending in order, something like this:
Father
Mother
son, then daughter, (but siblings are about the same level above any female spouse)
male spouse
female spouse
their children last
If your MIL comes from a culture/family like that, she really may not be doing anything personal. It might be how she was raised. It you think of it, she probably wasn't considered of much worth in her family and marriage to her parents and in-laws. She was just the lowly appendage on the totem pole. Probably why she is so cold and distant. Sad really when you think about it.
If you do decide to do this for MIL, make sure it's not motivated by the need to
finally get the reaction you have been hoping from her. She won't suddenly become warn & fuzzy and acknowledge that you did this for her. She probably wont even mention the present or the effort you put into doing this for her. Make sure you aren't setting yourself up for disappointment in doing this for her.