Does a dream after performing Salatul-Istikhara mean that Allah is pleased with this marriage and that it must be accepted?

There is no obligation to accept a suitor. However, if he is a man of good character and religious commitment, then he should be accepted, based on the Prophet's (peace be upon him) saying: "If there comes to you one whose character and religious commitment you are pleased with, then marry [your daughter] to him. If you do not do so, there will be tribulation on earth and widespread corruption." The fiancée's reluctance does not mean there is no good in marrying him. Rather, the matter should be entrusted to Allah Almighty, and istikharah (seeking guidance from Allah) should be performed. Visions have no connection to istikharah, even if one feels comforted by them. If the marriage takes place, then there is good in it, by Allah's will.