If there is a will, it must be probated. Richard Winblad is the expert on the forum on that sort of thing. If no will, then there are other proper ways to get it done. It is well worth the money to do it properly and establish her title.
Yes, if current royalties, then upon the probate documents being presented and filed in the courthouse, she will get the payments. You might want to go ahead and contact Marathon and Rimrock and find out what they will require to put her into pay status.
If there is an executor, then the executor should hire a licensed engineer to give an appraisal value as of the date of death. If the increased density cases were already at the OCC then my engineer says that should be included in the value. When a person dies, the asset values are “frozen” as of the date of death. If the original person had a very low cost basis, then they could pay high capital gains if they sell. If you don’t get the cost basis set, the IRS will say it is zero and have to pay capital gains on the whole amount (another reason not to rush right now).
Any existing lease may or may not control deeper drilling. If the lease had no depth clause, then it will control the deeper drilling. If the lease had a depth clause that released the lower zones, then a new lease will be needed. If included in a force pooling, that is another issue which I can clarify later.
You have weeks of work to do here, so don’t let anyone rush you or try to grab those royalties away from you. You have the potential for not only the currently known wells, but perhaps future ones. Just a note: I am a big believer in all members of a family getting up to speed on learning about their mineral rights. NARO (National Association of Royalty Owners) and the forum can be tremendous resources.