Q: 2 iphones vs. 1 non-iPhone = (iMessage vs. SMS)

My wife and I have iPhones my mom used to have one but decided to switch to another brand.

when ever she sends a group text to both of us we receive it just fine, however when we try to respond it automatically sends as an iMessage.

My wife and i receive the response in the group, however my mom does not since she does not have an iPhone.

And since the message was received (by other iPhone), it doesn't give us the option to send as text. In fact the only way to respond to the group chat is my going into my settings and turning iMessage off.

Which is a pain in the butt, and messes with setting everywhere on my computer and ipad, and its just a pain.

Is this a setting problem?

or is apples setting of "always send as iMessage unless it can not be delivered" the one to be blames for this?

I really need to know if anyone else has encountered this before!?

I tried to deregistered my moms number for iMessage thinking that's the problem, but the database came back saying it was not registered with an apple ID.

Im stuck!

Any help would be greatly appreciated.