Not knowing what college you’re referring to, makes it hard to cite specifics, but in general:
Most colleges have a very strict set of requirements in order to meet in-state tuition eligibility. Your mom getting a job in the state is typically one such requirement BUT you will still need to prove Indiana residency for 12 months before applying. They will look at things like where taxes are paid, where vehicles are licensed and registered, residential history. It’s at their discretion whether or not to grant it and you can usually appeal if the decision doesn’t go your way.
If it’s a college where you think you’ll be a candidate for a high merit award, sometimes that can get it down closer to in-state prices.
Anyone who I’ve known to be granted in-state status based on a parental move has only been granted it for the last year of college (maybe the last 2 years if things move quickly). I wouldn’t drag your feet with getting vehicles set up in the new state.
Here is the University of Indiana’s policy, in case that’s the college you’re referring to. If not, a quick Google should take you to the info for your college.