In the play The Effect of Gamma Rays on Man-in-the-Moon Marigolds by Paul Zindel, the character of Beatrice represents a repressed, abandoned, and frustrated mother of two whose financial and social limitations render her hostile and bitter towards those around her.
This is because, as her character progresses, it is evident that she lacks the basic skills to redeem and better herself as a woman. Instead, she takes the easy road: she dwells on the past, becomes dependent on alcohol, complaints, and goes to great lengths to make life miserable for those who are closest to her. In colloquial terms, Beatrice epitomizes the phrase "Misery loves company".
Tillie, as a foil of Beatrice, possesses the same amount of zeal and determination as her mother. The difference is that Tillie uses her zeal and determination to succeed, while Beatrice uses it to destroy. The way in which Beatrice tries to bring Tillie down is by not sending her to school hence limiting Tillie's talents, by threatening to kill Tillie's beloved rabbit, by complaining to the teacher about the "radiation" project, and by belittling and reducing Tillie to a kind of house servant. In the end, Beatrice inflicts the heaviest blow by killing the rabbit, after all. This is her most evil and imprudent act. And why not do it on the very night when Tillie wins the prize for her science project?
Ruth, who is the most affected of the sisters, is too weak and too used to her mother to resist her. Beatrice is just as relentless with her and uses Ruth as her psychological punching bag. Ruth has to listen to her mother's past mistakes, her wishes and frustrations, and her complaints about life to the point of Ruth's breaking into seizures. That is how evil and toxic Beatrice's effect is in her own daughter.
The eponymous "Mr. Goodman", as his name implies, is Tillie's teacher and mental salvation. Of course, Beatrice must be a witch to him as well and she does this by calling him incessantly at school to complaint about the treatment that he gives her daughter (which is kind and healthy, by the way), to complaint about the project, and just about everything she can think of. She is rude to him and tries to emasculate him by deeming his looks "effeminate", and "weak". Since Beatrice lacks the intellectual ability to overpower Mr. Goodman, she resorts to low blows and silly, petty, and catty name-calling and whining.
Dr. Berg, the school principal whose mere intervention is to tell Beatrice about Tillie's successful entry into the science fair, also gets his share of Beatrice's wrath. This time, he invites Beatrice to sit in front of the audience as a way to support her daughter's presentation of her project,and to accept whichever award Tillie gets. What he gets in return is a semi-deranged woman on the other side of the line screaming how she "will think about it". This is because both, Dr. Berg and Mr. Goodman represent the faction of society which is bound to uncover Beatrice for what she really is: an abusive and unstable parent. Yet, Beatrice cries after she offends people. Perhaps she has hit a bottom low where she cannot help herself any longer. She may just be a "crazy woman."
Therefore, Beatrice's lack of self-esteem, dignity, and purpose in life make her take her frustrations on the successes and hopes of others. She is like a tumor, so to speak: she hits, hurts, and branches out to bring everything on her path down with her. She is the archetypal antagonist.