Yes,
there will definitely be potential high level conflicts and this
doesn't apply only to Christian, but to Islam and all other
religion that generally support/are advised to have relationship of
the same religion.
A friend (who is a christian) told me that her christian
friends obstracized her when she has a bf who is not a
christian
And I am branded as Evil. 
***
Its a karmic hurdle the couple have to go through - its not about
the environment or the external factors because they are just going
to keep coming - its about the state of mind, your strength, your
ability to hold on, solve problems and blind faith to believe.
Every relationship has their own unique problems - for cases like
this: it would be this issue.
Cheers
