I agree with Lynda and Dallace on the Ancestry hints. By all means check them out, but don't believe them without proof.
As for Rachel Lamar and Rachel (Unknown) Miller, the profiles don't provide any reason to believe they match. The only things they have in common are first name, approximate year of birth, and state of birth. Neither one shows a source for any of those facts. I looked in FamilySearch, and found no record of Rachel Lamar marrying Mr Miller. Miller's son was born in 1827 in Georgia. If Rachel Lamar was executrix of her father's will in 1840, she would have been recorded as Rachel Miller (Was she? No copy of will or link to it provided.). Finally, the 1850 US Census showed a Rachel Lamar, age 50, living in Randolph County with Margaret Johnson, 59, and Hannah Lamar, 18. I think you have to rule her out before matching Lamar-276 to another Rachel.