What is the ruling regarding the fast of a wife whose husband fondled her during the daytime in Ramadan, and the husband ejaculated while not fasting due to a legitimate excuse, and the wife was fasting?

If the wife is free from the emission of maniy (seminal fluid) or madhiy (prostatic/vaginal fluid), her fast is valid. However, if maniy is emitted from her, her fast becomes invalid, and she is obligated to make up for that day. The same applies to madhiy according to some scholars. Engaging in foreplay is prohibited if it is highly probable that it will lead to the emission of something that invalidates the fast.