I'll try:
For 2018 the TPs filed MFJ with 3 qualifying kids.
EIP 1 was paid to them before the 2019 returns were filed.
So that meant they were eligible to get EIP 1 of $3900- (1200+1200+500+500+500) based on 2018 filing.
Each now single partner reports exactly half of what sent. That is $1950. (3900/2) So that looks correct.
Some confusing elements-
You say "They got the first stimulus ..."
then you say
"... she never got .. the first payment." ??
Also, not sure why the other party is saying their EIP 1 was $2,200.
I'm seeing confusions also among my post-EIP-divorced clients.
Miscommunications, misunderstandings, closed bank accounts, new addresses, mailed checks not received.
Confusions ....