My boyfriends mom hates me.what now?

I've been wiht my boyfriend nearly 4 years,and his mom hates me.
We're in a long distance relationship,We dont see each other very often,but I can honestly say I love him.Last Christmas,he went out and bought me a necklace from Zales,and a teddybear,His mom refused to let him send it, [[he didnt have his liscence at the time,so he asked her to give him a ride to send it out at the post office]].She told him that he shouldnt be with me,because he cant see me,and Im probably cheating on him anyway.She tells him to stop wasting his time on me,and find someone better.
I really dont understand why she doesnt like me.I've been nothing but nice to her,even after finding out she hates me.Im very polite,and I respect her very much.
I've tried talking t her about it,she says she doesnt know what im talkng about,and that she doesnt dislike me at all.[[Obviously,thats a lie.]]

well I dont now.
some people are like that, shes just got to learn your trust...of being with her son.
she assume shes love`s him very much? + wouldnt want him to get hurt. so your`ll probley need to earn her trust ?

but dont you think 4 years strong isnt anough to earn trust?!
I mean,damn.