I have an intern who helps me code data and metrics I'm measuring from Qualitative Usability Testing sessions. However, we have a deadline and she has been out of the office more than I'd like or expected her to be (another story). Would it invalidate the testing if I jump in and code some myself? Would we both have to code all of them, or can I code half and she codes half? I feel like that's a variable I shouldn't add to the results but project scope and deadline are of importance!
Without knowing more details I assume you and your intern share an approach and protocol for your analysis and review. Are you both working from the same definition of what does or doesn't qualify as a theme or pattern, etc?
Qualitative data analysis is inherently subjective. As long as you share an objective approach to analysis, it shouldn't matter too much if you have more than one person contributing.