Holm has much of the right skill set to beat Rousey in that she has a lifetime of boxing footwork and boxing at range. She also has reach and is a pretty big and strong woman relative to the weight class.
However, the #1 problem that Holm has is she lacks power in her hands. She's not known for having an especially damaging jab or punch and leg kicks are extraordinarily risky against a grappler like Rousey.
In my view if you want to keep Rousey on the outside you'll not only need the footwork and technique, but you'll need to generate sufficient power to hurt Rousey enough that she's not going to just ignore your strikes and close for the clinch. Without that power, it's a losing battle.
Sure, I can see Holm evading Rousey on the outside for some period of time, but winning a decision on points for 3 rounds is a completely different animal than winning a decision on points for 5 rounds. 25 minutes is a really, Really long time to evade the clinch with Rousey. And the problem with Holm is that it only takes ONE clinch for Rousey to effectively end the fight.
Some people have been yammering about Holm not being ready... the problem is that Holm will NEVER be ready. No amount of time in the gym will turn a boxer into a good enough grappler to stop a life long Olympic Judoka from tossing them on their head. If Holm had a strong wrestling or Judo base that would be one thing, but coming from Boxing and ZERO grappling it's just NOT enough time. Holm would be in her 40's by the time she had even close to the level of skill necessary to stop Rousey from putting her on the ground and submitting her.
Essentially Holm's best chance at a win is a KO from a head kick. And the odds of landing that kind of head kick without it getting caught/avoided and Holm ending up on her back is pretty darn slim.
Holm's particular skill set is very good in some areas but grossly lacking in terms of grappling. Without the ability to close the skill gap in terms of defending the take down, then her only real path to victory barring a lucky kick to the head is pretty much trying to jab/dance for 25 minutes. And I just don't see that happening unless she develops significantly more punching power.
Holm is just facing a really bad match up in Rousey. She'd honestly have a much better chance if the champion was more of a striker ala JoJed or Chuck Liddell than against a grappling heavy champion like Rousey.