Scales of Time by Viola Grace

Working for a scaled merchant takes a turn when her ancestor decides to stake a claim on the only human on his world. She strikes up a friendship and works toward romance. He goes straight for romance.

Kris missed her friend when they parted ways, but continuing to work with the merchant they had been contracted to is still fun. Controlling the blazing heat that she emits under duress is also awkward, but she manages. Her boss has provided her with a series of items to make her life easier.
Now that they are on the merchant’s homeworld, Kris finds out that her allergies are threatening her life, as about seventy-five percent of the foods are out to kill her. She is careful, but as none of the locals are allergic to anything, they don’t take her situation seriously.
A sudden trip to medical care results in scans that let the local Hmrain know she isn’t just a visitor. Overseer genetics are in her body, and they just need a little something to get them started. Essan flexes his wings and looks at the alien, making a decision that will change his life and hers. For eons.