what was Eliza reaction when Wickham was engaged

Do you mean engaged to Lydia? By that point she doesn't think too much of Wickham. I think she fears for her sister. Mr. Darcy finally pays Wickham's debts to give Lydia a fighting chance at respectability.

i meant engaged to Miss King

In a letter to Mrs. Gardiner Elizabeth relates that Mr. Wickham's affections for her have subsided and have been transferred to another young lady, Miss King, who recently acquired 10,000 pounds. Elizabeth concludes that she must not have been in love with him, because her feelings are still cordial toward him.