Group Chat between Samsung Galaxy S4 and Nokia Lumia 520 (I Think) problems - tech help?!

Group Chat between Samsung Galaxy S4 and Nokia Lumia 520 (I Think) problems - tech help?!
Added (1). So my there are four people in this situation. Me, with an Samsung Galaxy S4, my brother and sister, both with iPhone 5, and my mother, with a Nokia Lumia 520 (I think). When a group chat is started between us four, I cannot see the messages from my mother - they appear as if a text was sent, but no characters were typed. However, I CAN see the messages from my brother and sister, whom can also see my mothers.

Does that make sense?
Any advice/ solutions would be greatly appreciated!
Added (2). My brother, sister, and I are all on Sprint
My mother is on Verizon
Added (3). UPDATE - M moms phone is Nokia Lumia 928

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