Hi. Very sorry to hear one of your robos died. The other one will live quite happily alone - in fact many pairs end up needing separating when they fall out and start fighting which happens a lot. So no, don't get her another companion - because only sibling pairs can live together at the best of times.
I would suggest doing a cage clean and changing the substrate - not just in case of disease, but also to remove the scent of the other hamster. That will help her move on and accept the other hamster is gone.
Generally a full cage clean, doing everything at once, is stressful for a hamster, but sometimes it's necessary. So I would remove everything, disinfect the cage and wash any contents that are washable - eg plastic or ceramic. Any wood items would need to be baked to disinfect them, or replaced.
Johnsons petsafe disinfectant is good - but rinse well afterwards to remove the scent.
https://www.amazon.co.uk/Johnsons-Cl...gateway&sr=8-2
Do you have somewhere to put your hamster while doing the cage? Eg a pet carrier? Or another small cage temporarily?
After cleaning and replacing all the substrate and washed items, you could maybe add the odd new toy, so it's still familiar but slightly different (even if just a new toilet toll tube!) and also scatter feed to distract her. Plus a big pile of plain white toilet paper strips so she can build a new nest.
She might need leaving alone for 2 or 3 days after the clean to settle again. I would then not clean anything for two weeks so she has the full settling in time from scratch again.