I will exclude moments that can be seen as only friendship moments, no romance intonations at all.

[spoiler]
1.) When he dragged her along in Hargeon and told her to 登録する Fairy Tail
2.) When she held him back during the Lullaby arc
3.) In Galuna Island when he saved her from the poison
4.) When he went for her rescue in Phantom Lord arc
5.) When he caught her when she was falling out of the tower and she yelled out his name, being sure that he would be there to catch her.

(OMAKES)
link
1.) Happy in Boots: She's a princess and she falls in 愛 with him without even knowing him, but he has become barbaric...

Chapter 1!

Lucy entered the guild thinking about the last job she went on, not noticing the heavy atmosphere. As she entered the hall a hush went over the guild. Watching as her フレンズ threw her worried looks she searched for Natsu. She looked around but he was nowhere. At least nowhere she could find him. She ignored the onlookers and headed towards Mirajane. She was the only one not 芝居 weird she thought.

"Hi Mira, what's up with everyone? They are 芝居 strange." Lucy said. "Don't あなた know? It's that time of year." Mira 発言しました winking. I don't know. Which time of 年 is it?" Lucy asked....