The ABA Model Rules of Professional Conduct, which every state but California uses as the model for their own rules, say:
The comments to the rule explain:1.4(a) A lawyer shall:(1) promptly inform the client of any decision or circumstance with respect to which the client's informed consent, as defined in Rule 1.0(e), is required by these Rules;(2) reasonably consult with the client about the means by which the client's objectives are to be accomplished;(3) keep the client reasonably informed about the status of the matter;(4) promptly comply with reasonable requests for information; and(5) consult with the client about any relevant limitation on the lawyer's conduct when the lawyer knows that the client expects assistance not permitted by the Rules of Professional Conduct or other law.
[A]lawyer who receives from opposing counsel an offer of settlement in a civil controversy or a proffered plea bargain in a criminal case must promptly inform the client of its substance unless the client has previously indicated that the proposal will be acceptable or unacceptable or has authorized the lawyer to accept or to reject the offer.As to whether the lawyer has to accept the client's decision, the rules are clear:
(a) Subject to paragraphs (c) and (d), a lawyer shall abide by a client's decisions concerning the objectives of representation and, as required by Rule 1.4, shall consult with the client as to the means by which they are to be pursued. A lawyer may take such action on behalf of the client as is impliedly authorized to carry out the representation. A lawyer shall abide by a client's decision whether to settle a matter. In a criminal case, the lawyer shall abide by the client's decision, after consultation with the lawyer, as to a plea to be entered, whether to waive jury trial and whether the client will testify.Relaying the settlement offer to the client isn't a just a formality - it's a requirement. It's not that hard to write the scene correctly. The proper response is, "I'll relay it to the client, but I'll recommend against it." The only way the lawyer can shoot it down is if the client already said they wouldn't accept anything under x-amount and authorized the lawyer to turn down anything under that number.