Can my Mum be one of my dependent since I assisted her financially for 10months before she did received her Unemployment benefits?

If your mother had more than $4300 of income in 2020----at any time in 2020----then no, you cannot claim her, even if you helped while she waited for her unemployment.

CREDIT FOR OTHER DEPENDENTS

https://ttlc.intuit.com/questions/4499708-what-is-the-500-credit-for-other-dependents-family-tax-credit

https://ttlc.intuit.com/community/children-dependents/help/what-does-financially-support-another-person-mean/00/26532