How would you feel in this scenario?

You are girl 2. You're single and alone most of your life.
Guy is madly in love with girl 1. Girl 1 is madly in love with guy.
Girl 2 is a casual friend to guy. Guy has made it absolutely clear to everyone that he intends to marry girl 1.
Girl 2 wishes them both all the best and is very supportive of the marriage.
After several years, girl 1 decides to break up with guy! Then she suggests that guy get involved with girl 2!
How does that make you, as girl 2, feel? Second fiddle? A stand-in until girl 1 changes her mind or guy wins her back because you know he's still very much in love with girl 1?

Guys, if your heart was dead set on girl 1 and no one else will ever do, would you be able to just suddenly switch over to girl 2, especially if you hardly have anything in common and none of the plans you had with girl 1 would ever happen with girl 2?

How would you feel in this scenario?
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