I echo much of what others have said. Patience, and being open are good ways to deal. Give her a chance to figure out what is in this for her. She might want someone all to herself or may see benefits to sharing you with another. She needs time to think that all through. Its fortunate that your situation can offer that.
What's your girlfriends view on it all? After all, she is a part of this equation also and has some experience in what you might be going through. Perhaps she can be a confident in your process?
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