h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I once a girl who said she was a diagnosed split personality, but did not have multiple personality disorder. She was split three ways (oddly enough, the two "other" pesonalities identified as male, not unusual considering she is bisexual anyway), but was generally aware of what each personality did. In fact, they sometimes actually held conversations with each other, and two of them (the two males) didn't get along well together. While sometimes one of the personalities would do something without the others knowing, as a general rule all three knew what the others were up to.

Any thoughts?

although you speek of split personalities, it is not that they are separate. The reason they develop is to deal with tough and stressful situations: they help another alter to deal with the situations. Maybe in this case the alters didn't develop all the way and kept in touch with the ego (the person) and eachother. It can happen that an alter does things that other alters don't approve off, because they 'think' it'll harm the person they are guarding..
MPS/DIS is a strange, difficult disease just like the mind/psyche in which the disease develops. The mind works in mysterious ways!
About the male alters: men can be considered to be stronger and bigger than girls. To keep her head up in stressful situations, maybe your female friend developed male alters as she thought they would be more of a match against the stressor.

A diagnosis of Dissasociative Identity Disorder requires some significant disassociation and memory lapses and such between the identities - as such it's possible to have a 'split personality' (or 'multiplicity' or 'be a multiple' or ...) without being DID. Seems like this could be the case with this girl...

is there any way to deal with this condition or to minimize the intrusion from alts without seeing a doctor or taking drugs.

Sure. Plenty of folks have either ceased to be multiple, or obtained a state in which their multiplicity is not a hinderance.

I recommend reading Multiple Identities & False Memories: A Sociocognitive Perspective by Nicholas P Spanos. It has some interesting sections on multiplicity displays in history and other cultures, showing that it does not have to be a dysfunctional state. It also has information about the influences that make displays of multiplicity less frequent and less overt.