Facts we know so far:
Name: LEK/R
7/18/1969~DOB: (assumed)
1987~ Moved from Az (Scottsdale) to Tx (DFW)(presumably)
1988~Applied for Tx SSN: 458-99-xxxx
1997~Graduated University of Arlington
1/2004~Married JBR
2008~Had a daughter
12/20/2010~Divorce papers Served
12/24/2010~Commits Suicide
Sounds about right. If anyone wants her full SSN, it is available on the SSDI if you look her LER name up on FamilySearch.
Also, we can assume that the identity she stole was of someone that really was born on 7/18/1969 (since she'd need the birth certificate) and, as a child, would have died before turning 18 though most likely younger than that. Also, that way FLEK would be more sure the child had never had a SSN.
Another consideration is that I've always heard that for identity theft, people usually use someone that was born in one state but died in another, so that there is less chance someone will match the records. Probably a bit different now that it's all searchable, but in the 80s this is something that would have been considered. This is pretty important if we're assuming that the UID 'took' her identity in Arizona - the child she took the identity from must have been born in Arizona, but it is possible the child didn't die in Arizona?
So the two scenarios I lean toward are:
A) FLEK, living in State (or Province of Canada possibly?) X, and knows or knows of a child named LEK, who was born in Arizona but dies in State X. How FLEK/UID knows this child is unknown, it could be anything from a family acquaintance to something in a newspaper. FLEK then decides to take this identity at some point, and travels to Arizona, gets the birth certificate, and starts off on a new life in Texas.
B) FLEK, living in Arizona, knows of a child named LEK who was born in Arizona and possibly known to her in Arizona, but has now died somewhere out of state. Maybe she hears it down the grapevine, gossip, something. She then gets the Arizona birth certificate there in Arizona, and goes off to Texas from there.
Or if we find out that the real LEK was born in another state other than Arizona, then just replace Arizona with that. I really think that the way to find who the UID is, would be to find where the real LEK really was born, and also where the real LEK died if it is a different state. Most likely FLEK is originally from one of those two places, how else would she know about this child? The only other way she would know about this child is if it was the child of a family member or family friend, and that would be a risky identity to steal.