DId Snape Ever Have A Chance?

During the Battle at Hogwarts, Snape is murdered by Voldemort and Nagini. Before he dies, however, he is able to pass on essential memories that will prepare Harry for his essential death by Lord Voldemort. Harry immerses himself into the memories and learns that he is a Horcrux and must die. More interesting, however, is what Harry sees about Snape's relationship with Lily.
 
From the very beginning, it is clear that, as a child, Snape was completely smitten by Lily because she was special and different, just like he was.

Lily appears to be interested in Snape as well because he was the first and only wizard she had ever met due to her status as a Muggle-Born. Snape had all the answers she needed and his presence was likely a comfort to her -- proof that she wasn't crazy and that she really was a witch.

From here, the movie shows their relationship severing when Lily is sorted into Gryffindor and Snape into Slytherin.
     It is important to note, however, Lily is considered to be unfailingly kind to everyone -- no matter what house they were sorted into. So it is highly likely that she would still strive to be friends with Snape. For example, in their later years at Hogwarts, Lily defends Snape while James, her future husband, and his friends harass Snape in front of everyone in the courtyard.
     The point being that Lily continued to maintain a friendship with Snape after their first year.

What happened then to end that relationship if it didn't have anything to do with them belonging to rival houses and Lily meeting James (like the movie leads you on to believe).

The answer is simple.

One word.

"MUDBLOOD" 

 Even though Snape was being embarrassed and there were most likely his pure-blood friends were around, using that word on  his oldest, best ((and only) friends was completely out of line.
     There are just certain things you can say without losing the friendship. For Lily, that word was "Mudblood." She might have been able to ignore it from anyone else, but not from Snape her first magically-gifted friend who had been through so much together.

The question must be asked then -- What if Snape never called Lily a "mudblood"? Could they have gotten married and have children of their own? After all, he did love her and she could have had similar feelings until he opened his big mouth and ruined everything between them.

We'll never know for sure though, but I would like to think that maybe they could have had a lasting friendship at the very least.