The humorous and loyal best friends is a staple in romance novels. She seems to have personality but she exists solely to make the main character feel like everything she says is fascinating.
But is she really great if she's completely unrealistic? Who is really so outward looking? A character having the pure selflessness of a saint is especially annoying when we already have a main character who suffers from the burden of being perfect.
Can you tell I agree with Jane Austen that "pictures of perfection make me sick and wicked"?
To me, shiny happy people can fall in love in about 20 pages. The 300 pages only happen when the hero and heroine are kept apart by external obstacles like misunderstandings and world wars.
In real life best friends are often a mixed bag. Sorry to say something so unpopular, but we all have a cousin who's best friend ended up sleeping with her husband. Many have felt the sting of being dumped by an adored 'best friend' who finds a newer, cooler bestie. When everything goes wrong with your wedding or birthday party or prom, your so-called best friend is usually involved somehow. You assume she'll do the right thing but ... this assumption leaves you without a ride home late at night.
The fallout of having a best friend can be so painful that you regret that you ever opened your heart so completely. If only I'd kept things more casual. If you didn't think she would always be there for you, it wouldn't have been so devastating when she moved across the country with her boyfriend of three months. Ultimately it's too much pressure to expect so much of a friend, who has her own welfare to worry about.
I believe in life partners with whom you share your life, but my relationship with my husband is a very complicated relationship that is not all about taking and one-sided perfection. Enormous compromises have been made -- I can't move to Paris if the opportunity arises unless this change can someone fit into his life. We make each other better people by challenging each other -- unlike the literary best friend who is always there to kowtow to the heroine's needs and goals and quirky whims.