No, that's okay - feeding to sleep is useful, but it's another thing to wean them off, so it's probably as well you don't. The idea is to encourage the baby to teach itself to fall asleep without parental help - but that's difficult to do under 6months old.
The book I suggested has ideas you could try to at least point your LO in the right direction.
On the nap front, you may actually find that more napping will help her sleep better at night - baby sleep is weird in that if they are overtired, they sleep worse. Half an hour isn't really long enough to do much more than a quick battery recharge, rather than deal with underlying tiredness. Having said that, it's the devil's own job to get a baby to nap for longer if they're not inclined, so don't beat yourself up if it's not happening!
You're doing the right thing to encourage her to have a longer nap at lunchtime - but she may actually need 2 hours or more and then another hour in the afternoon so she's not too tired to sleep properly at night. Sounds topsy turvy, but that's often the way of it. Try offering her more nap chances or doing what you can to leave her sleeping for longer in the day. It may well help with the nights.
Also, try for a bedtime no later than 19.00 (if you don't already) - again, overtiredness can often strike if the baby doesn't get to bed in good time.
Getting out with the baby in a sling/pram is good for both encouraging naps and sleep at night (there's not much else you can do to entertain them at that age, anyway!) - a bit of fresh air can work wonders - and on you, too.
Do you have a fixed bedtime routine? Bath, lullaby, feed, bed etc.? That can help signal to the baby it's time to sleep. Have you tried baby massage?
The thing is, as I said before, you're almost certainly not doing anything wrong. Some babies are naturally inclined to be good sleepers and some aren't, whatever the parents do. Most of them (99 per cent) grow out of it sooner or later.
Sending solidarity in your direction!!