Issues with some possible users loading times

My Friend has trouble loading ourworld from the client because she has so many items, like: somewhere between 20k to 15k items. And the load times are like god slow, so she can never ever load from the client at all. Is this an issue with the client itself, or hardware specifications?

P.S: she can load from the website just fine mind you, this is the client-side where she's having issues from.

Maybe sell some items, or transfer some of them to other accounts. Not much else you can do.