At least Serena's feelings for Ash doesn't stop her from being upset with him at times which is ok, most relationships have faults, but little things like this make Ash and Serena's bond even stronger cause of how they deal with these faults. I mean even on Ash's part to not even get upset with Serena when she was sassy towards him about the cake was another way of seeing how much he's matured. Now there is nothing wrong with Serena being shy around Ash from time to time, but she will have to open up as well if she's ever going get Ash to notice her feelings, cause as of right now Ash still needs to get used to her sassy side, which he's handled well so far.
I mean Serena already used to Ash when it comes to his kindness, determination, love of food, pokemon, training, and gym battles, since episode XY 25 Serena IMO seemed to understand how Ash feels emotionally when it comes to his training and gym battles, which is another thing that's special about Serena's feelings for Ash. She also follows his words "Never Give Up Until The End"
Ash is used to Serena's love for fashion, baking, and out of all his female companions Serena has been the nicest to him and him as well towards Serena. Also Ash has shown a side of himself that I don't think he has with any other female companion, he's been shy around her. Now it's true that the XY saga has brought some major character development on Ash's side even on his bond with Serena.
Now another thing Serena could do to progress Amoushipping is maybe admit to someone about her feelings for Ash, but who would it be?
Look at all this support this shipping is getting, all I'm saying is everyone here is supporting this shipping in their own way and that is amazing and to every Amourshipper that's a part of this thread or in any other way towards Amoushipping thank you! There's also one fanfic I think you should read called "The Way To Ash's Heart"