dress for a wedding

[inlectorecumbit]

Help !!
I have no dress sense at all but this is not about me.
DD is attending a wedding at the beginning of April, Her BF is the best man for his brother.
Where can she find a reasonably priced dress?? She is only 5 foot tall and approx 9stone although is trying to lose a few pounds prior to the wedding.
She has been looking on line at chi chi .Does anyone have any suggestions for her please.
I am a complete slob normally always in Jeans and T shirts

Budget?

Style?

Opps sorry forgot that bit.
max £150.
Style would be nothing too fitting/clingy.knee length so l guess petite and maybe have to pay to get IT altered.
She hates her arms so it must have short sleeves and not showing cleavage.
Something similar to this?

French Connection is a good bet. I have this dress which I wore to a wedding, it’s gorgeous in real life.