If I let my mom claim me as a dependent, and I also filed separately, will I be able to get a stimulus check?

no,, you are not eligible.  and the decision to "let my mom claim me" isn't how it works.

(I assume you are over 17 and not in school currently),

what was you age on 12/31/19? what I really need to know to help you out is whether you were over 23 or under 24 on this date.

Your mom CAN claim you if she passes all four of these tests.  (Whether she claims you or not is her decision - not yours) . these tests are from your Mom's perspective.  You don''t have a say in the matter. 

1. The person either (a) must be related to you or (b) must live with you all year as a member of your household. (she already passes this test because you stated it's a relative)
3. The person's gross taxable income for the year must be less than $4,200 in 2019.
4. You must provide more than half of the person's total support for the year. (this means financial support for fair share of rent, food, clothing, transportation / car, utilities, medical costs, COLLEGE COSTS)
 5. The person must be a U.S. citizen, U.S. resident alien, U.S. national, or a resident of Canada or Mexico.

if she passes all 4 tests she CAN claim you. if she FAILS ANY ONE test, she CAN NOT claim you.  And you have to respond on your tax return that someone CAN claim you if all 4 tests are passed, EVEN IF SHE DOESN'T CLAIM YOU.  She has an option; you don't. 

if she CAN claim you, you are not eligible for the stimulus (even if she doesn't claim you).  if she CAN'T claim you, you are eligible for the stimulus

post back and we can go from there.