"It is a great joy for her."
Translation:C'est une grande joie pour elle.
"plaisir" isn't a verb, it's a noun. However "faire plaisir à" is a very common idiom in French which translates to "please someone".
"Ce cadeau me fait plaisir!" = "This present pleases me!" = "I'm very happy with this present!"
However, " C'est une grande joie pour elle." has a stronger meaning than "Ca lui fait plaisir"
Hope it's clear enough
Keep in mind that "une grande joie" is feminine and "un grand plaisir" is masculine.
If you incorrectly suggest "un grand joie," Duo can and will suggest that you use "plaisir" (or "bonheur") instead of correcting your article and adjective. The Duo algorithm is unpredictable in that sense.