I think she just runs because she’s overwhelmed and needs to be alone for a moment, and when she calms down she can think of an actual plan for leaving. With this in mind I think the scene works as it is. When she stops in the forest she doesn’t have a clear plan, just a feeling that she wants to get away. Before she has a chance to think any further BB-8 shows up, and she tells him she’s leaving. Then when she sees the attack she realizes she can’t leave her friends behind.

Your idea removes the “leaving” part, which I guess might make it easier to accept that she then goes back with BB-8 without much motivation (before she knows about the attack), but I feel like the point of her running into the forest in the first place was to show her strong urge to leave. So if we remove the idea of “leaving” the running away might seem even more random.