$500 seems low if she needs a whole new bumper and paint. Sounds about right if they're going to fix the existing bumper and respray though. Who wrote the estimate? Insurance company? Body shop? Presumably she's not a fault here since she was hit from behind, so let the insurance companies worry about cost. Tell them what you want and make them get it done.
'15 i3 REX // Capparis // ZGW // ZTD // HK // 20"
20% Tint, Coding, LED High Beams/Signals, Painted Reflectors, MAX2 Hardwire
Past: F30 335i, E90 328xi