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Yes, I agree with Lazur that it sounds like a performance issue related to possibly several different things specifically, but large file size in general. One good thing, is that using layers can is a good way to help alleviate the problem.
A 14 mb file will challenge Inkscape on almost any computer system. Filters and as far as I understand, imported raster images, need to call on the cpu, to be displayed/rendered. But otherwise, Inkscape uses the system RAM to function. So the part of the problem related to a large number of nodes (for example) probably can't be alleviated with changing the core threads setting or other filter display options. (At least that's my understanding.) How much RAM in your friend's system?
For a multiple core system, Inkscape has a way to use them all, as opposed to just one. Note that I barely understand about the cores and stuff, but I do know enough to explain how to set Inkscape to use them. Edit menu > Inkscape Preferences > Rendering > Number of Threads. Your friend should put the number of cores in that field. (And then restart Inkscape, as noted.)
Also, on that same Inks Prefs page, you can find some other settings that could help with filters, if you're using filters.
Here's a tutorial/article I wrote to help users identify the problems areas for performance, and learn how to work around them. I tried to include all the basics, but if there are any particular steps you want to discuss in detail, please feel free.
Tips to Avoid Performance IssuesActually I've never heard of or experienced snapping as contributing to performance issues. Snapping can be affected by performance issues, and it can make snapping hard to use. But as far as I know, snapping doesn't contribute to the problem. I could be wrong, but I haven't seen any bug reports about it.