The structure of $[\mathrm{B}\mathrm{e}{\mathrm{F}}_4{]}^{2-}$ is tetrahedral
The Be atom is $\mathrm{s}{\mathrm{p}}^3$ -hybridized.
Electronic structure of beryllium in $\left[\mathrm{B}\mathrm{e}{\mathrm{F}}_2\right]$

[Two unpaired electrons form covalent bonds ( $\mathrm{\sigma }$ -bonds) with two F atoms]
Electronic structure of beryllium in $[\mathrm{B}\mathrm{e}{\mathrm{F}}_4{]}^{2-}$

[Two ${\mathrm{F}}^{-}$ ions, each donate an electron pair into empty $\mathrm{s}{\mathrm{p}}^3$ -hybrid orbital forming a coordinate bond].