Mel, I would carry on, as David's Mum says--you've come this far! There's almost always some regression when you try to change a habit. Many 5 month olds need one or two night feeds. We don't df and we have a night feed between one and three a.m. most nights.
In addition to regression from not bf to sleep, taking three hours to settle is likely a timing issue--either too tired or not tired enough. As you're trying to change the habit, it's probably overtiredness. However, I would keep an eye on total sleep and keep in mind that you can't make her sleep more than she needs to. If you know the amount she was sleeping in a 24-hour period prior to putting her own EASY, know that may be the correct amount of sleep for her within an hour or so. Putting her on EASY helps develop healthy sleep habits, better quality independent sleep, and helps YOU to get some rest when she no longer needs you in the night, but it can't make them sleep MORE than their need. Just something to keep in mind. When she's sleeping independently she'll settle into a pattern that includes the right amount of sleep for her own needs--so keep focusing on teaching independent sleep and don't worry SO much about timing, as that will sort itself out once she learns to sleep completely on her own.
Hope this makes sense! You're doing a GREAT job--keep it up and let us know how you're doing!