Hi Sharon,
At 5.5 weks it is still very common for your lo to have 2 night wakings. She will let you know when she is ready to drop a feed, and will do so by sleeping through this feed.
I would not worry too much, and would feed her a this age if she wakes up.
Have you tried cluster feeding in the evening to help her take a few extra calories before bed? This could help her sleep through the dreamfeed and enable you to give it to her while she is asleep.
Hope this helps.
Paula