Although people think there are 'wheelchair privileges,' that does not exist.
For situations where a guest with a wheelchair does not use the regular line, it is because the regular line or boarding is not accessible.
As Joanna71985 posted, most attractions have Mainstream Lines, which are wheelchair accessible through the regular line. So, in most cases, you will just enter the regular line with the wheelchair.
Strollers are not allowed in most lines - there are stroller parking areas outside/in the area of each attraction. Other than a few attractions, you will need to park your child's stroller before entering the line.
The Safari at AK, Fantasmic at the Studio and Bug's Life at AK are examples of attractions which allow guests to enter the line with a stroller and then have stroller parking partway thru the line.
When you enter the park, pick up a park map for Guests with Disabilities. There is one for each park and they are located with the other park maps in the map kiosks at the park entrance. Look for the blue wheelchair symbol on the bin where the maps are; the map has a wide black band on the top and says it is for Guests with Disabilities. The maps list the "Mobility Access" for each attraction. In most cases, it says to "Enter the Standard Queue" . For attractions with Fastpass, it most of the time says "Obtain a Disney's FASTPASS or enter the Standard Queue."
All of the attractions at the Studio and AK are Mainstream (accessible) lines where guests with wheelchairs wait in the same line with everyone else; most at Epcot are also accessible.
MK is an older park and they were not able to make accessible lines for some attractions. In those cases, the map or CM at the attraction entrance will tell you where to go to wait. Even if it says to enter through the exit, you will probably still wait the same or close to the same time as other guests.
There are also some attractions where the boarding area is not accessible, but the line is. In those cases, you will wait in the regular line to a certain point and then will be directed by a CM or a wheelchair symbol to go somewhere else.
For situations where guests with wheelchairs are directed somewhere else, the guest with a wheelchair and 5 members of their party are usually able to remain together.
For those attractions where you want to ride, but she will not be, you would just go through the regular line. In some cases, she would be able to wait with you in line, but then would bypass the loading area and go directly to the exit.