I wouldn't straight up use the ativan on it's own on days without the klonopin. I suggest lowering the klonopin dose and supplementing it with the ativan.
Divide the number of days she needs to have the klonopin pills last her by the amount of mgs left, and break&take the pills accordingly. Then use the ativan to supplement the klonopin, using the dosage conversion to figure out the dosage needed to equal the remainder of the daily dosage needed.
The reason why I suggest doing this instead of just having her take klonopin on its own until it runs out and then just taking the ativan is because of the properties specific to each benzo, meaning that she would not be getting the specific relief she usually gets from the klonopin if she is solely using the ativan.
I am not sure what specific properties each one has, but an example is that if one of them has strong hypnotic effects and the other one doesn't, then she would not be getting the sleep aid that comes with hypnotic effects on days that she only takes the one drug without that property. This is just an example though since I don't know which properties are specific to the benzos are mentioned, but I'm sure you get my point.
This is the best advice in this thread IMO.
Benzodiazepines can't all just be used interchangeably contrary to popular belief. When I was extremely dependent on alprazolam (Xanax), I couldn't substitute anything for it. Believe you me, I absolutely exhausted every other option, diazepam (Valium), clonazepam (Klonopin) which has never worked for me, it's useless to me, indistinguishable from a breath mint. Even IV lorazepam (Ativan) couldn't stop the withdrawal syndrome/seizures. Yes, I was taking probably exponential amounts more than most people ever would. In just one day, taking what others take over 1-3 months of modest use.
However in my defense, I am still sticking by my all-benzos-are-NOT-created-equal theory, and thus cannot be used interchangeably verbatim. To back this up, prior to developing such a large tolerance, clonazepam still felt like a placebo to me, and lorazepam was also disappointing.
Nothing short of the triazolobenzodiazepines, such as my prescribed triazolam (Halcion), worked while I was getting off alprazolam, which of course,
is a triazolobenzo.
I don't know if I'd bother with a police report for something like clonazepam.... Talk to the doctor first, if that's what he insists on then sure, but in my experience psychiatrists are more than comfortable helping out their patients in times of need like this, and often don't need a police report if there is doctor-patient trust. It's not a highly controlled substance, just a Schedule IV, it's certainly not the same as running out of Schedule II pain medication early, for which police reports are most often necessary.
I'm proud of you OP, very happy to click on this thread and be surprised to find someone attempting to provide care for their family, rather than some kid who stole their mothers Klonopin, which sadly, is what I was expecting when clicking this. Very pleasant surprise, I thought I was going to have to give the why-you-never-steal-peoples-benzos speech. Good luck man, Tommyboy outlined the same strategy I would do given those circumstances.