Yes, it's a doujin ending as she wanted.
My friend told me. It's her plan. She know the problematic chapter 129 will be in the last volume (14) and if she ended Grapara badly, the volume 14 sales will be in trouble. So, she planned to use the chapter 132-135 (full sex scenes of Shinobu and Fumi) to compensate it.
The old plan was, we'd not see Sakura in chapter 132 because it's dedicated to the sex scenes to sell the volume 14. But after the plan was changed (with some reasons), she added Sakura and Nagi to chapter 132 and cut the sex scene short to end in chapter 133. My friend told me since chapter 132 that the coming of Nagi and Sakura will create at least another volume (15), not end at volume 14 as formerly planned. Kodansha might do something to her before chapter 132 came out.
Just my friend's assumption, we'll see whether there is really volume 15 (chapter 138-147). It she can't fix the problem, volume 15 will be the last.
@diphuc1 let's see.