ifindedout gave a streetview locaton, here's an aerialview:
28°18'28.7"N 81°34'13.2"W · Celebration, FL 34747
PayrollNerd, further back in the thread it's noted that
she was a diabetic and it's believed she didn't have any
medications with her.
When she turned left (eastwards) out of the restaurant on
Irlo Bronson, she (perhaps drove to the 7-Eleven on the
corner of that highway and Poinciana Blvd to refuel and
then) perhaps proceeded north along Poinciana Blvd to get
onto the W Osceola Parkway (where it is known a toll was
generated by her vehicle that date). (A 'pay-by-plate' toll?).
Here's the view she would have seen proceeding westwards
along the W Osceola Parkway (if her intention was to return
to her residence away to the north, via the I-4 'East'):
Google Maps
I wonder if she was unfamilar with the area and mistakenly
took the 'next left' which leads you towards the I-4 'West',
instead of proceeding further to the I-4 turnoff going
eastwards which was the correct way to return home.
As you can see, there is no I-4 'East' sign, instead there is
a sign for 'Disney World'. From that point, the I-4 East
turnoff is about 1.3 km straight ahead, and the 'Disney
World' turnoff is more than 3km straight ahead!
So assuming she took the incorrect 'next left', she would
have proceeded on State Road 417. On toll road SR-417
there is a way to get onto I-4 East via Celebration Ave,
but unfortunately, again, there was no 'I-4 East' sign to
advise of that possibility:
Google Maps
There's a toll booth on SR-417 she would have had to
drive through. (I wonder if the text seen in your post:
FL - FL - Sandra Lemire, 47, Orlando, 8 May 2012
"Last week, detectives from Orlando Police provided
additional information that prompted this weekend’s
search", could this refer to some other possibly
discovered toll information for her vehicle on her
disappearance date?)
Proceeding further along SR-417 does lead you to the
place where her vehicle left the road into the pond.
Speed? A lapse into a diabetic coma? We'll never know.