Welcome to Justanswer! I am Dr. Altman and happy to assist you both today!
Very likely the berry will not cause her any harm but best to know what to montior for including lethargy, vomiting, diarrhea, reduced appetite, breathing heavily... if you note any of the above please consider a veterinary er, especially with not knowing what berry exactly was ingested best be safe...
One article lists toxic red berries:
Daphne ( Daphne spp.) is a fragrant flowering shrub that grows in U.S. Department of Agriculture plant hardiness zones 5 through 9. The four-petaled flowers range in color from white, pink, red or light purple. Once the flowers fade, bright-red single berry clusters are left behind on the branches. All parts of a Daphne plant are toxic, with the highest concentration of poison found in the bark, sap and berries. The poison is so potent that a small child can die from ingesting only a few berries. Symptoms of Daphne poisoning include headache, nausea, diarrhea, convulsions and delirium.
Japanese Yew ( Cephalotaxus harringtonia ) is an evergreen shrub that grows in USDA zones 6 through 9. Instead of cones, yew plants produce supple, scarlet, single-seed berrylike fruit. The yew berry is easily identified by its cupped shape that holds a large single seed inside. The pulp of the berry is harmless if ingested, but the seed, needles and twigs are all highly poisonous and may cause death. Symptoms of yew poisoning include difficulty breathing, trembling and lowered heart function. Death can occur with no prior symptoms.
Bitter nightshade (Solanaceae dulcamara) is a vining plant that grows in USDA zones 3 through 9. You can identify bitter nightshade by its simple leaves and white or purple flowers that closely resemble those of potato or tomato plants. Highly invasive, bitter nightshade is classified as a weed and commonly grows along fences and roadsides. The single, egg-shaped, orange or red berries of the nightshade plant grow in clusters. Berries are most toxic when they are green and unripened. Symptoms of nightshade poisoning include blurred vision, fever, hallucinations, extreme thirst, convulsions and death.
English holly (Ilex aquifolium) is an evergreen tree that often grows as a shrub in USDA zones 7 through 9. Recognizable for its glossy, green and yellow leaves and bright red, orange or yellow berry clusters. English holly is an invasive plant and spreads aggressively when not monitored. Seed, bark and leaves are mildly toxic, but the highest concentration of poison is found in the berries. Symptoms of holly poisoning include dizziness, lowered blood pressure, nausea, diarrhea, elevated heart rate and stomach pain.
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