I don't like Meadow as a name at all. It just doesn't appeal to me. I do like Willow somewhat - I wouldn't use it but I don't mind seeing people named Willow.
Meadow and Willow have the same ending sound and are matchy, but they aren't too
similar - as in, I don't think people will be mixing them up because they can't keep the names straight. I personally wouldn't use them together even if I did like Meadow, unless one was a MN, because I don't really like matchy names. I think it's a little too much, especially if there might be future siblings with nature names.