I'm thinking of using the baby name my SIL was planning on using for her baby
Will you use that name without telling your sister in law?
I'd like to meet SIL and discuss this with her so we can all be part of the decision.
That sounds like a good thing. It is wise to discuss with others when there could be a potential conflict over naming your baby. You want to use your SIL's baby name so you should ask her if that is okay.
Why do I have to go through the hassle of doing all that. I just want to use the baby name.
Yes, but as you said before, it was your idea to meet with her and talk this out, and I hope that you stick to that plan. Your sister in law might have a deep connection to that name, and that might be why she wants it for her own child. Alternatively, she might just like the sound of it, and she might let you use it.