Awwwwww thats sad but i really like it.

The Marguerite, or oxeye daisy, is fairly common and totally harmless so I'm not quite sure what your point is here :/ In terms of writing, your grammar is not perfect but competent enough. Congratulations :) However, your writing style is suffering from a case of beige prose. For example:

"Her boyfriend was sick so Maggie decided to get him flowers. She found the daisies. She brought them to him. Then he changed."

and again,

"One day he disappeared. Maggie looked all over for him. Eventually she turned to researching the daisy that she had brought him. It took her weeks to find out anything. When she did Maggie was distraught."

These short choppy sentences are very blunt and don't really enhance the story. There are no details, so the reader is limited to picturing a stark sterile scene with no real personality. This coupled with the perplexing purpose of the story just kind of leaves the reader going "Huh?" at the end.

I love the ironic idea of a depression inducing flower. The writing was clean and imaginative.

Nice work!