The bride hunt / Jane Feather.

Enhanced descriptions from Syndetics:

Hailed for her captivating blend of romance and sensuality, New York Times bestselling author Jane Feather has enchanted readers and critics alike. In this second book in her dazzling new trilogy, Constance, Prudence, and Chastity Duncan, London's most charming young matchmakers, are faced with a ruinous lawsuit - and it's up to the brainy, beautiful middle sister to extricate them.
No sooner had the Duncan sisters' Personals service turned a profit than their controversial newspaper, The Mayfair Lady, offended a powerful earl - who is now determined to ruin them with a lawsuit. In dire need of counsel, the women turn to England's most-sought-after young barrister.
Sir Gideon Malvern is notorious for his aggressive style - and his love of a challenge. Spirited Prudence, with her beauty unsuccessfully hidden behind spectacles and frumpy clothes, provides him with exactly that. But how in the world will the Duncan sisters be able to afford Gideon's fee? Prudence proposes a barter- Gideon defends their case; they find him a bride. It's an exchange of services even this most cynical, single barrister can't refuse.