الكلمة الصحيحة هنا هي: أنا أدعو لك بالشفاء. While "I pray for you" is used in English, in Arabic we don't use it's exact translation because as Anvar said; praying is for Allah only. We also say: "I remember you in my prayers" which in my opinion is much better than "I pray for you" and gives the right meaning.

نحن نقول : شفاك الله أتمنى أن تتعافى قريباً

The term "أصلي لك" is not used in Standard Arabic, but it's used in Egyptian Arabic as "بصليلك". It's more of a Christian term in Egyptian Arabic. The more used one is "أنا أدعو لك" or "أنا أدعو لك بالشفاء" to emphasis the kind of prayer you're praying to the person. In Egyptian Arabic "بدعيلك" or "بدعيلك بالشفا". Get well soon! :)

بدعيلك صج لكن بيصلوا لله بس

أنا اسف / أنا اسف لسماع هذا ana aasif / ana aasif li samai-i hatha أدعو لك بالشفاء العاجل adu-uu laka bi-shifa-a al-ajel