Am I providing my personal information / MariBank account information to Shopee when I access MariBank services from Shopee app?

No. Once you are redirected to the MariBank login or signup page from the Shopee app, you would be accessing the MariBank platform exclusively. Everything you do here (including your account application and accessing your MariBank account(s)) would be on the MariBank platform and all your information would be kept secure by MariBank and separate from Shopee.