No. You absolutely can NOT put her in with a dwarf hamster that isn't the same kind as she is. Dwarf hamsters have been known to kill other's that aren't their own kind. Try to find her a companion that's also a campbell russian, because dwarves should be kept in same-sex pairs, but under no circumstances should you mix breeds.
The age shouldn't be a big problem, just make sure they're the same breed. Though putting her in with a baby might not be a grand idea. Also, before putting anyone 'in' together, make sure to do proper research on introducing dwarf hamsters, and the quarantine period before you do so (to assure that the new companion doesn't have a fatal disease she could give your Mocha). I know with rats there's a multi-step procedure to introducing new ones, starting with putting their cages near each other, then switching the cages so they can get accustomed to the smell, and such like that. But again, this is for rats, The procedure may be different for dwarf ham-hams.
Good luck!