When the Cullens eventually mover on, will Renesmee pretend to be Bella's sister o will they go with the semi-truth, that Bella is Renesmee's mom?

Probably. Bella and Renesmee did registrarse the family at the same time, so it would kind of make sense to call them sisters.
But I always thought that they'd say Edward and Renesmee were twins; they look exactly alike so that would fit too :)

They would have to make Nessie Bella's sister because Nessie will stop growing at 17 and Bella's corazón stop at 19 and nobody can have a kid at the age OF 2. So they can't go semi truth.

thats strange
tu dicho that bella being renesmees mum as the semi-truth
how is that?
that is the real truth not semi

wow! good Q! never thought of that!! well i guess they wld pretend 2 b sisters o well i don't think since she wld be with jake, and jake has apack, well i don't think that the pack is going 2 mover around with the vamps, and besides renesmee isn't full vampire so she cld live with jake and visit the cullens now and then! anyway thats just what i think!

thats a tough question..
they can go two ways..(in my opinion)
1) they can say that Renesmee is adopted..
2) o they can say that Renesmee are sisters..