Well, if Thalmarkin had just accepted Fronen aid there wouldn't have been a problem! While Richard holds respect for King Fingolfin and has no ill will against Thalmarkin, this all went on under 'Well, they refused our aid and don't really care about us apparently'. Keep in mind that Richard is a relative new Noble in Beluaterra and doesn't have much knowledge about the whole past political scene. He hailed from Old Grehk, and believed the Alliance with them was the highest priority. But Richard believed to have pretty good relations with Old Grehk, he was convinced he could discuss the subject in private. Thalmarkin would have never heard about it unless Old Grehk would give Fronen some sort of protection in his eyes. And, of course, he wouldn't simply have approached Old Grehk by directly asking them the question, he knew it was a sensitive issue. And if Old Grehk rather wanted to attack Melhed instead (For Richard, it would have been most sweet to do WHILE the war was going on, just to annoy Thalmarkin. He believed you guys deserved a poke back for poking by refusing Fronen's aid, he had to push the whole thing through the Senate after all!), it never would have been openly discussed.
Keep in mind that this would never have happened if Melhed couldn't hold their own against Thalmarkin anyway. Richard was in no way willing to burn any bridges over this (Unless it involved sticking out his tongue to Thalmarkin, Richard wouldn't dare do anything more then that!), especially not with Old Grehk.