i think its better to play it aggressive because: 1. You can, since jiggs outmaneuvers her and 2. I don't like giving her room and time to pull turnips
it sounds like you are doing the bair too early, just again really make sure ur hitting with the very tip (practice in training mode) and to avoid getting dash attacked, the second you land from your bair do SOMETHING
this is one of the things that seperates mid-high level jiggs from mid level jiggs (i guess? the point is its really good)
always do something after your attacks, its normal to just land and shield but thats TERRIBLE... the second you land JUMP IMMEDIATELY and BAIR... or immediately just jump away, or immediately dash away
now that ive said that... you can go watch some vids on youtube and you'll notice that top level jiggs are always doing something right away when they land or just choosing not to land and continuing to stay in teh air while doing more aerials
well like i said, upairing her high up is pretty hard, what you want to do is recognize when she is too high up for you to get to her and don't waste ur jumps... try first just jumping to a side platform and then maybe the top platform instead of going straight at her, so that you will get a full 6 jumps from the top/side platform and be able to go higher
if she really is too high and just waiting you out, there is no rush in killing her, just wait for her to come down and then guess/react to where shes going and try to catch her with an aerial
side platforms just really help in these types of situation, so lemme know if ur using those and if u think they'll help
ok, so if you are afraid to go behind her because of dsmash, you shouldn't be going for uptilt... either go for all falling upair on her, or just use another jump and REST THE DSMASH... its kinda tricky to space, but if u practice ull get the hang of it
uptilt is more used when she's shielding, since then she cannot dsmash, she can only grab or roll or jump oos, all of which lose to a properly timed uptilt (at first just doing it immediately when u land next to her sheild will probably work because they will panic, but once they get used to it, they will start to wait and ull have to guess when they'll try to get out of shield)
I used to be terrible vs turnips until i foudn out nair cuts straight through them... just try it, nair completely wrecks her because it goes through the turnip and hits her, also like i said, i try not to play too defensive and allow them to pick a lot of turnips, but it'll still happen a lot no matter how you play
oh also, after writing this i realized that some of these questions are answered by idea in the mu guide on the first page, you should check that out if u havent yet:
http://www.smashboards.com/showthread.php?t=298777