Step 1: Translate the relations into algebra.
Let Veena’s share be $V$. Then Amit paid $A=\tfrac{2}{3}V$.
Veena paid half as much as Tanya, i.e., $V=\tfrac{1}{2}T ⇒ T=2V$.
Step 2: Write the total bill in terms of $V$.
Total $B = A+V+T = \tfrac{2}{3}V + V + 2V
= \Big(\tfrac{2}{3}+1+2\Big)V
= \tfrac{11}{3}V$.
Step 3: Fraction of the bill paid by Veena.
\[
\text{Veena's fraction}=\frac{V}{B}=\frac{V}{\tfrac{11}{3}V}
= \frac{3}{11}.
\]
\[
\boxed{\tfrac{3}{11}}
\]