film related question:
my boss was telling me she was trying to get pictures of her son playing baseball and the pictures were coming out blurry...i asked what speed of film she was using and she said 400.
Need faster shutter speed to stop action; requires larger aperture on lens to allow in more light to allow for faster shutter speed.
However, eventually you reach a point where the shutter is wide open and there's still movement. (Also wide open will affect how much "depth of field" there is, that is, how much of the photo is in focus. Generally shooting a large aperture will mean that objects distant from the subject may not be in focus. If she focuses on her kid at the plate the 3rd baseman in the background may be out of focus).
You can increase the sensitivity of the film (by using faster film), allowing you to increase the shutter speed even more.
However - doubling the film speed only gets you a 1 stop advantage; if you were shooting ISO 400 film with the lens wide open using 1/250 shutter speed, going to ISO 800 film will allow you to to shoot at 1/500 shutter speed. That may, or may not be enough to stop motion.
Doubling the film speed has penalties in grain - the faster the film (all else being equal) the more grain there may be in any enlargements.
(One of the advantages of DSLR's - you can change the "ISO" on the fly w/o changing rolls of film).
The first place to look is at her lens - how fast is it? If she's shooting one of the ubiquitous 70-200 mm zooms with a max aperture of 4.5, she's handicapping herself out of the gate. Put in a faster lens (say, 2.8) and you can shoot at a higher shutter speed, stopping more motion.
She can, as you suggested, move to a faster film; if she's not looking at extreme (over 8x10) enlargements then grain may not be an issue.
Also, she can set the camera ISO at 800 even if she's using 400 speed film, and tell the lab to push the roll 1 stop; however, this would apply to the entire roll of film, not just the ones she takes at the ballpark. It takes some practice and a decent lab.
Assuming she's not willing to invest in a new lens, has no decent lab, and has only "slow" film with her, she may be able to "cheat" a bit by using a flash on the camera (note you can't use this trick from the last row in the bleachers - but from closer range it can work magic. Sometimes.)
which is source of quote below:
"The third example of using flash is to stop motion. Because the duration of a typical flash is very short (anywhere from 1/1000 to 1/50000 of a second) it can be used in combination with a slower shutter speed to freeze the action in a frame
But realistically - ISO 400 is pretty doggone fast, should be fast enough for outdoor daylight ballgames. I'd recommend that she put her camera on full manual, open the lens up to the max aperture and then set the shutter speed to whatever her light meter recommends.
And shoot from a tripod for a few shots - her "motion" blur may turn out to be camera shake.