Good afternoon Avi W,
Welcome to the Apple Support Communities!
I understand you have set up Family Sharing with you as the organiser and you have invited your sister, who has on an Android to share your Apple Music subscription. The resource below explains the requirements for your sister to set up Apple Music on her Android phone and join your family:
Join Apple Music on Android
"If you don't have Google Play in your country or region, you can download the Apple Music app from Apple.
Apple Music features might vary by country or region. Learn more about what's available in your country or region.
Before you join
- Make sure that your device has Android 4.3 (Jelly Bean) or later. To check your Android version, go to Settings > System > About phone.
- Get the Apple Music app from Google Play.
- Know your Apple ID, which is the account that you use with all Apple services such as the iTunes Store or App Store. If you don't have one, you can create one when you join.
If you previously joined Apple Music on an iPhone, iPad, iPod touch, or computer, learn what to do."
Get an Apple Music Family subscription
Set up Family Sharing
Take care.