Do you think Elena will feel differently after she becomes a vampire and realizes that Damon HAS COMPELLED HER?

Damon does truly love Elena. Him compelling her to forget the "I love you" thing was him being selfless with her, and his brother. He knew Elena loved Stefan, and vice versa. And, at that time, Delena hadnt had the development it has now, and Damon knew she didnt have strong feelings for him at that time, and he knew he wasnt at a good place mentally for her. He was very unstable and under a lot of emotional stress. Its because he loved her so much is why her compelled her to forget.

Damon compelled Elena only twice - the first time they met he didn't have any feelings for her, he just wanted to keep his presence at Mistic Falls in secret, I think it was very natural that he used compulsion to make a total stranger to forget their conversation.
The other time, he proved he loved her. He desperately needed to say "I love you" out loud, I think anyone can understand why. But he also knew, that if Elena would remember that she would be sad. confused, probably even a little guilty that he fell in love with her. Back then she was completely in love with Stefan, she wasn't ready to bear Damon's feelings toward her. He didn't want to cause even bigger mess in her life, that's why he decided to make her forget. That was really selfless of him to keep hiding how he feels about her to keep her happy.
Will Elena feel differently? Probably so. But I don't think it will be mostly because she'll remember the "I love you" moment, even it will probably really touch her. I'd say it's rather becasue vampire's feeling & emotions are intensified - she'll be even more lost fighting her feelings toward both brothers...

Maybe she'll understand him more when she gets them memories back, i think(not straight away) she and Damon will become closer and she will have an inner battle with herself regarding if she made the right choice or not. She will have to think about her decision fully, about both Stefan and Damon and what she truely wants.

The first time Damon compelled Elena, the night her parents died, that was self-serving, however in 2.08 ("Rose"), Damon compelled Elena to forget because he believed Stefan deserved her and he did not. Regardless, he still needed to tell her that he loved her. I'm not sure if you realize how difficult it would have been for Damon to make Elena forget his confession of love. I didn't see it as self-serving at all, I viewed it as a great sacrifice on Damon's part.
I think Elena will not be mad at Damon. I also think that the realization that Elena did meet Damon first and how Damon had her pegged from the second he met her ("You want a love that consumes you....") will change things between the two.