The Value of Friendship

Earlier today (a few minutes ago, actually) a friend of mine who is spending time with my ex (who's a friend of hers) was talking to me via Windows Live Messenger.
Now, in all honesty, I have no issue with either of them except my ex for the simple fact that she's my ex.

We were having an average conversation, despite the fact that I knew there had to be an ulterior motive as to why she was talking to me in the first place, especially considering the fact that she was spending time with my ex.
I discovered I was correct on this assumption when she asked me if I'd ever be friends with my ex again. I was caught off guard and a little annoyed due to the fact that this was uncalled for and it was obvious she was speaking for that ex of mine, and that was the only reason she was really speaking to me in the first place.

I told her that I knew she was going to ask something along those lines, and she apologized, but continued; I told her that I might be an occasional acquaintance and we would chat with each other sometimes, but I didn't think we would ever be friends again. She then proceeded to ask me if I thought that was a waste of a friendship, and made it obvious on her part that she did. I said I didn't think anything was being wasted if nothing was there anymore, and then, get this, she said this to me: "well w.e. if you don't see the value in a friendship, I'm not gonna bug u about it. each to their own."
This wasn't a rude or irrational comment, but it did still offend me as it seemed as if she was suggesting I found no value in friendships; no, I don't see any value in a friendship between ex's, but that doesn't mean I'm her enemy, it just means I won't be her friend.

I see strong value in friendship and believe friendship is one of the few main factors which hold society together. I, like most people, have a main best friend and then another few best friends who I often spend time with when I get the chance, and I also have good friends, ok friends, sort-of friends, and acquaintance's.
Some people don't seem to understand this structure (as is obvious), and I'll explain it:

Acquaintance's are people I know and know of, and will occasionally chat with and/or have met or been introduced to, but are not someone I see as a friend. In fact, these sort of people could easily swing either way; they could easily become a 'sort-of' friend or someone I dislike/ an enemy.

Sort-of friends are people I've met and have grown to like and will tend to chat with them time and again when I encounter them, but I don't consider them a direct part of my social group and rarely ever spend time with them in school, and never outside of school.

Ok friends are people I have grown to like to quite a thorough degree, and will occasionally spend time with them in school (such as during class projects, P.E. activities, or even occasionally at lunch break for different reasons).

Good friends are people to which I like alot, and spend time with quite often during school and on occasion outside of school, and I deeply appreciate their input in anything, and their opinion on any matter.

Best friends are people which I have grown to love and understand (in a much different context then it would be in a actual interpersonal relationship) and who I spend most of the time with in school, and very often outside of school. These are people who I believe will always be my friend in some form or another, and to whom I will never forget if for some reason we can't or don't continue our relationship.