Tenant bounced two checks and won’t pay certified funds

[Mary T.]

Live in Texas and have a minor setback with a tenant. She’s had two bounced checks so we asked to pay in certified funds for the remainder of the lease (3 mos). Her response: “I don’t have to. My lawyer says I don’t. I will pay with a check and I will mail it. Stop harassing me!” My concern is she will mail it on the 3rd and we won’t get until two days later and once we deposit it may or may not clear. What to do? Feeling trapped by a tenant. Any advice is greatly appreciated! Thx