Undergrad vs Grad Prof Recommenders

[rainy_day]

I'm halfway though my MA and I have a question for the forum regarding LORs. Obviously, the majority of my letter writers will be profs from grad school, but I'm wondering if it is a good idea to have one letter from undergrad? I worked really closely with one prof in undergrad (I took lots of classes with her, and she was the reader for my honors thesis. Heck, we had dinner last week, and I'm dog sitting for her next week.) So I know she'll write a really excellent letter for me (she did for my MA applications) and I'm 99% set on asking her. But, is there some secret stigma associated with such a letter that I'm unaware of?