S.V.
J.,
It is great that you want to be a good friend, we all need those. Perhaps if she does not feel comfortable putting her child in a toddler bed yet, you can explain to her that you just have no room to store it. If she wants the bed to use in a few months, or whenever the child is ready, she will need to find a place to store it until then.
If she doesn't want to do that then you can feel better about selling it, if your friend wants the bed she will find a place for it. Then any child rearing issues will not come into the picture, she won't feel you are pushing her to put her child into the bed if she doesn't feel they are ready.
Best of Luck,
S. V