Could just be the stables brand. I've seen smiley faces and hearts as brands...not sure how easy tracing it is going to be unless its some super stable over there that's really well know. I'm not aware of a brand database, but someone else on here I'm sure is more knowledgeable about that.
She has RJ on her left shoulder. The J is an extension off the R. She also has 810 and 8 on her left hip...but those I think are just ID numbers (like cattle tags) since she was from a PMU farm. The RJ puzzles me though.