The relationship of 我 and 咱们 In a current commercial ad of bird's nest aired by China's National Radio, two women identified as former classmates had the following conversation:

甲：我妈快70岁了，我要买礼物回去过中秋。

乙：是呀，好久都没见到咱妈了。。。。

It is clearly the two speakers are not sisters or daughters of the same woman which they both call mother, but 我 and 咱 are both first person nouns, what is the relation of the two words? Does one of the speaker try to endear herself to the other?
The meaning of 咱 is different in northern China and the rest.


In east-north China, 咱 is the same as 我. People there say 咱 to refer
to him/herself. And it depends whether the speaker is endearing
him/herself. This usage is actually a little bit weird for Chinese
from southern areas.
In the rest provinces of China, 咱 is different from 我。咱 refers to the
both sides of a conversation, and is often used to show closer
relationship or endearment. 咱 is much less frequently used than 我们
there.


So in your example, I think this conversation happens in east-north China since 咱妈 is rare in southern area and it simply refers to 我的妈妈.