"She has a horse."
Translation:उसके पास एक घोड़ा है।
You always put an ए before the word पास:
मेरे पास, तेरे पास, उसके पास, उनके पास.
If you want to know why, it has to do with something called the 'oblique case'. Basically when you attributing something to a noun the noun changes. For now it's probably easier to not worry too much about it.