Yearling Filly and Mare problems

Question
I just recently bought a yearling Paint filly. She was found on her last owners property abandoned in a dog kennel. She does not act abused. She seems to have all the basics taught to her so far for her age. Not sure if she is even quite 1 year. Very friendly. But when we go to feed her she pulls her ears back and kicks out at us and starts to eat then starts pawing at the ground then holding up her leg. I feed her in her stall. Also, the filly each day when I turn her out goes into my mares stall and urinate. Is this normal behavior? I am afraid to let her loose with my 7 year old mare in the pasture. When they meet nose to nose she gets a little aggressive and then my mare  reaches out to bite or nip her. I really don't want to have her hurt. Do I let her out with her or wait an amount of time before I do this? My mare is very gentle and she was recently split with her pasture partner and gelding, after 3 years of being together, when i purchased her. I thought she would accept her. I do understand the alpha horse dominance and it will have to be understood who it is between them, but will my mare get hurt by the filly kicking her or my filly get hurt from my mare. Also my mare has never had a foal. My mare is also a paint.
Thanks so much for your help. Ramona, NC

Answer
Hi Ramona,
I can't tell the future but I can say that I'm sure they will have some scuffels and then end up being good friends.  your mare is alone and so is this filly and I'm sure they would rather make friends then try to kill each other.  I can't tell you if one will hurt the other as all things can happen but I would think you'd want to take the chance so they can have a happy social life together.  Her returning to the stall to urinate is natural behavior, she is leaving her scent as well as doing what comes natural when horses are kept in stalls.

Take care and watch them close.  I'm sure they will be happy together in no time.

Jeff