- The "Resistance" appears to have been "real world" only
- She was surrounded by this "Resistance" when meeting Wade in real life
- The "Resistance" is likely disbanded at the conclusion of the film
So after getting a chance to rewatch the film I thought I would take a stab at answering this a little bit more clearly. Before I start I would like to reinforce my initial comment about how drastically the film and book are different. While it is the same plot and many of the same details the similarities end there. All the details in this answer will regard the movie only, unless I state otherwise and I think the book will help explain better...
First, some background regarding IOI and their business practices because they are key to Samantha's motivations.
IOI operates a number of indentured service centers; known in the RPO universe as loyalty centers. These loyalty centers are a big chunk of IOIs business model and we learn from Sorrento and F'Nale during their business meeting after Wade wins the first key that the revenue they earn dwarfs the hardware division sales by a significant margin.
Even more important, we also learn from F'Nale that IOI purchased all of Samantha's debt (without her knowledge) and were therefore able to place her under "corporate arrest" and into a loyalty center (without her consent). This would present the idea that despite someone's best attempts at only purchasing non-IOI products and services to avoid the possibility of loyalty centers they can still have their debt purchased by IOI from a willing lender and find themselves forcefully (and legally) enslaved by IOI for life.
That said Samantha is known as Art3mis, the Sixer Fixer. This is undoubtedly due to her obvious distrust and hatred of everything IOI stands represents both in the OASIS and in the real world. In the film she informs Wade that her father got into debt with IOI and was sent to a loyalty center. While attempting to repay his debt (and away from his family) he got sick and died.
In the real world Samantha is surrounded by a "Resistance" that is opposed to IOI and attempts to live, support, and protect one another. Additionally, the group also appears to live "off the grid" as the only way IOI is able to track them is a lucky snapshot from one of their drones that captured the unique facial tattoo of the individual they believe helped Wade escape the Stacks. This appears to be a group merely trying to evade IOI and their indenturement teams.
Futhermore, the Resistance is not mentioned in the OASIS and it would appear that the group is primarily an "offline" organization. Art3mis never appears to be working with anyone outside the "High 5." Also, within the compound we see there are only two treadmills that grant improved mobile access to the OASIS; which would indicate that only one other player could easily "keep up with her" in the simulation. Additionally, when Aech retreats to fix Art3mis' motorcycle she turns to Parzival and (IMO) shows some contempt at the idea that he and "shoulder blades" are "claned up."
All of these points to me seem to reflect how we understand the character from the book to react to the idea of Gunter clans - which to be clear, she was 100% against.
To your last question of Samantha's faithfulness to her team I am confused. At the end of the movie, no one splits. We see her forcefully split from the Resistance upon her arrest by F'Nale, but that is also the last we hear of the Resistance.
After Wade wins the egg he splits control of the OASIS amongst the High 5 with their first action being to deny all of IOI's loyalty centers access to the OASIS, forcing IOI in effect to close them. What becomes of the individuals previously forced into lifelong debt is unknown, but it is a safe assumption that the Resistance would be disbanded as 1. Their primary goal was achieved and 2. Samantha, its principle member, was in a great position to ensure IOI would continue to be held accountable and kept in check.