What you're doing seems to be working.
Is there some reason to believe R doesn't know you're thinking of her and that you miss her? Has she expressed feeling neglected? Or are you just looking for solutions to problems that don't actually exist?
The fact that you're thinking about this means you're probably already doing plenty to reassure her. Assuming she hasn't expressed that her needs aren't being met, just keep doing what you're doing.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker