The DF goes until about 8-9 months or so. All baby dependant.
As far as 4 hrs, keep paying attention to her cues. Basically, it will be when she can go longer between feeds. Like if she wakes early from a nap, you don't necessarily need to feed her right away unless she asks for it. Although BW suggests 4 months for a 4 hr EASY, each LO is different. Some BF'd ones can't go that long until Solids come along, but we were able to go right at 4 months.
It does sound like she might be going through a GS. You'll keep having those along the way. You're doing great, and then you back track a bit, but then there is typically a leap forward.
HTH!