Almost seven months ago I moved into a new apartment with a roommate I really like. We have similar interests, humour, we bake, etc... I really consider her a friend at this point. When we first moved in we had little to no furniture and decided to go 50/50 on things and if we ever went our own ways would buy the other person out (if I leave with the couch I would pay her the other half) Well, everything went onto my credit card since I had the time to shop and once all was paid for, of course, her financial circumstances changed. Not only could she not pay half for shared furniture but she couldn't pay for her own personal belongings which I graciously picked up for her. Seven months later I've decided anything shared is mine and I'm okay with that, but she still owes me for her stuff (clothing organizers, shelving, desk...) I've brought it up a few times really casually but I'm moving out soon and need that money. How do I, without burning any bridges, make her understand the urgency?
I'm sorry to say you have been a bit foolish in this situation. Yes, something unclear happened to your roommate's finances, yes, you consider her a friend, but none of that changes the fact that she is taking advantage of you, whether she means to or not.
I wanted to publish your letter to serve as a pre-emptive measure to others who may be in a similar situation. The first rule of the roommate relationship is to figure out the money stuff fairly (and in writing) and stick to the plan. You did not stick to the plan. Instead you footed the bill for all the furniture AND somehow bought your roommate other things she needed. While that was very sweet and generous of you, it was not especially smart since, clearly, you also need that money.
You need to bring this up bluntly and explain that you need to be paid back now, before you move. I know you want to stay friends with this person, but if she can't pay you for seven months and she won't pay you now, I'd say she doesn't really want to. Go ahead and burn that bridge. I'm not exactly sure what kind of money we're talking about here, but you could consider small claims court.
Whatever ends up happening, consider it an expensive lesson and never get yourself into this situation again.