"Holler" means to call loudly, often across a house or yard. It also tends to convey a higher level of urgency.
"Holler me" is a combination of "tell me" and "summon me." It includes a stipulation that if you notify me of a previously agreed upon condition, I will follow through with the promised response. This is the same as "tell" but allows a higher volume and demand for attention. You don't have to raise your voice if you don't need to, but you're allowed to, and it's taken as a summons not a scold.
"Holler for me" means that I will come when you call, but when I get there, we'll have a discussion about what you want. It only includes answering the summons, not meeting another request.
That kind of subtlety appears in many Southern dialects of English, where prepositions do work that Northern speakers don't notice. (Northern dialects have their own bells and whistles, as does everyone's.) Southerners are often told to omit prepositions in certain phrases, which is aggravating, because most people don't have the linguistic expertise to explain what the darn thing does. But if you take it out, to a Southerner, there's a wobble there, like a chair with one leg a hair shorter; it's annoying and it can cause misunderstandings. Of course, these subtle distinctions are lost anyhow on someone who speaks a different dialect, but it makes a difference to the speaker.
I grew up in the Midwest but have Southern relatives, so my accent is bifocal. In Illinois, I sound mostly Midwestern. On a visit to Tennessee, I have a Southern accent as thick as molasses -- and oddly enough, it is also keyed by time and topic. Talking about certain parts of my childhood or activities such as fishing will turn it on. Just in case you were curious.