Women are emotional creatures, they will cling to anything/anyone that makes them "feel" what they want to feel for that given moment, whether it be happiness, sadness, or appraised. When women are single, they will clutch to other single friends to rationalize why they're single and how "better off they are" that they're single and they're "too good to settle down for anything less than perfect" etc.. you know, the typical BS that woman think.
As soon as a woman picks up a boyfriend that all changes (beta males do it too), because the relationship then becomes the source of their happiness. Women are also a lot more back stabbing then men.. it really all boils down to how they feel, or what they want to feel, they don't care who gets hurt in the process, even their BFFFFFFFFFFFFFFFFFFFFFFFFFFFFFForvever that they've known for years.