I know that I will probably get flamed for this, but that's ok.
I have never had any problems approaching with Ivysaur. In fact, I wasn't told originally that she is supposed to be defensive, so I played her, and still play her, very aggressively. Plus, and here's the weird part, that doesn't seem to cause me any problems. I can roll to approach with her, or dash into d-tilt, then go straight into Bullet Seed. Or, I can Razor Leaf spam until I get an opening to approach. I just play an aggressive Ivysaur, and that's not a problem for me. If I can get my opponent airborn, I try to get under them, right where Ivysaur truly shines. Plus, this gives me an opportunity for an u-air, which comes out faster than most opponents expect. Even the computer, which reads button inputs, can't dodge it! Does anybody else play Ivy like this?