I personally play her as OnHit similar to Kog Maw. She lacks Kogs range of course and her onhit just isn't quite as strong (87 max, vs 120 vs a 2k opponent). But she does have the following advantages:
a) The AP on Malady and even Nashers tooth are way more useful on her, than Kog.
b) Her onhit damage is permanently up, vs Kogs limited time duration.
c) Her spells are MUCH better, especially for an autoattacker's role. Her slow is incredibly strong, better than Kogs, she has the nasty Disable, and a self-shield/ranged nuke. her Ult is also ideal for CCing the typical enemy melee-er and boosting her survivability.
d) She benefits strongly from CDR due to her nice CC, making CDR items more viable (like nashers tooth as a 3rd item potentially).
This role requires you to play her like you would an AD carry. She ramps up much much faster than an IE/PD carry though, and brings her own CC.
Usual build of: Zerker boots, dagger to start, Malady, Wits End, Stinger, Phage, Ionic Blaster doodad (now buffed), ->Nashers tooth, -> Frozen Mallet.
The other way to do it is to tank up like crazy. An Ionic Boots, Frozen Heart maxes her CDR and lets her spam CC like few others, plus making her very hard to kill. Stack on the Odin, an Aegis, and a giant belt or two and she greatly contributes as a support, except she doesn't evaporate when focused like most of them...