Do You Have to Do Ghusl after Manual Stimulation?
Question

My question is: when is it obligatory for a woman to do Ghusl after being with her husband? More importantly, if they do not have sexual intercourse (penis entering vagina) and he just manually stimulates her, does she have to shower and perform Ghusl in order to fast the next morning?
Praise be to Allah.When is Ghusl required?
Ghusl is obligatory on men and women alike when one of the two following things happens:

When the two “circumcised parts” meet, which is penetration, i.e. intercourse – even if there is no ejaculation – because the Prophet (peace and blessings of Allah be upon him) said: “When the two circumcised parts meet and the tip of the penis disappears, Ghusl becomes obligatory, whether ejaculation takes place or not.” (Narrated by Abu Dawud; see Sahih Sunan Abu Dawud, 209)
Ejaculation – even if the two circumcised parts do not meet – whether this happens as a result of manual stimulation or otherwise. The Prophet (peace and blessings of Allah be upon him) said: “Water is for water” – i.e., Ghusl is required when water (meaning semen or sexual fluid) is emitted.

Can you fast without Ghusl?
With regard to fasting, it is not essential for a person to do Ghusl before Fajr starts in order for his fast to be valid . If one starts a day of fasting whilst Junub (impure as a result of sexual activity) the fast is still valid. (See: 70 issues related to fasting). But one should hasten to do Ghusl so that they can pray Fajr on time.
For more details, please see the following answers: 975 , 415 , 6010 , 82344 , and 93027 .
 And Allah knows best.