UGH! I recall when my dtr was born (3rd child) my boys were 1.5 and 3.5 yrs old and we tried squeezing all of them into our Jeep Cherokee. The infant seat we had was smallest at that time (narrow base), but even though the base fit okay between two toddler seats, trying to squeeze the actual seat into the middle and snap it in was almost impossible. And like someone else mentioned, the back doors had to be shut hard and my 1 yr old cried! We managed to put the two bigger seats side-by-side, but then the boys started pinching and biting each other! We ended up trading in for a used minivan...
But does her Focus have a passenger airbag shutoff? One of the toddlers could go up front as long as the bag is shut off. A pain to move later for an adult to ride, if the car seat stays in her car, though.
Maybe with the way gas prices are, and just the daunting task of taking two toddlers and an infant ANYWHERE will be enough to get her to mostly stay at the house! We only had the one car when my 3rd came along, and since my hubby only worked 5 miles away, I would either just stay home with no car all day, and wait to go grocery shopping (by myself!) once he got home, or if I HAD to have the car, we could take him back to work after he came home for lunch.
It is hard to manage with little kids and no car, or in her case, not really WANTING to go any place with three little ones, but it will pass soon enough, and now I desperately miss those times! Mine are 12, 10, and 8.5 now, and although no more car seats, lots more fighting and obnoxious behaviors to keep me from taking them into public together! HA! :D
Best wishes for a healthy child and hope you get the situation resolved!