Going a little more in-depth, Ivy has really good combo weight (as in: bad for us, good for them) which lets a few characters destroy us (such as falcon), to the point where just one combo can equal death.
Her recovery is subpar IMO. It's really glitchy, so sometimes it just fails when it should work, and it's really punishable by anyone who knows what they're doing. Unfortunately most people see the fact that they can't hog it and immediately dismiss it as unguardable and broken - when it really isn't. For example, mario can hold the ledge and drop-off bair as you snap up - or characters can simply force a ledge hop, which makes us vulnerable.
She has a great zoning game with leaf, fair, bair, dtilt, etc. however she can lose to characters with better zoning, such as Falco.
IMO, her worst matchups are (in no specific order): Marth, Shiek, Falco, C. Falcon, Lucas, and Kirby.