First as Mariam is a female name you should consider to use the feminine form:
رضي الله عنها (Radia Allahu 'anha)
عليها السلام ('alayha as-Salam)
Then radia Allahu 'anha or 'anhu (or rahimahu Allah) could be said about anybody you want to which them well, sahaba, tabi'yn, scholars, teachers, parents ... (see this Fatwa in Arabic)
And 'alayha as-Salam or the masculin form are usually used for prophets as... (See the following Fatwa in Arabic).
But be aware all these sentences or expressions are more a kind of dua' then a honorific title.
In the case of Mariam bint 'imran (مريم ابنة عمران) i found this Fatwa in which the scholar used the expression رضي الله عنها (Radia Allah 'anha, May Allah be pleased with her) instead of 'Allayha as-Salam when speaking about her! But on the other hand ibn Kathir and al-Qurtubi, say Mariam (عليها السلام) in their tafsir. In tafsir ibn Kathir you may read for example:
تفسير سورة مريم عليها السلام وهي مكية
Tafsir of the surah of Mariam peace be upon her which was revealed in Mekkah
While a Hadith quoted in Musnad al Imam Ahmad narrated by ibn 'Abbas (MAy Allah be pleased with both of them) our Messenger (Peace be upon him) himself honored his wife Khadija, his daughter Fatima and Aasiya bint Muzajim (the wife of Pharao) and Mariam bint 'Imran by saying Radia Allahu 'anhun and counting them among the best woman in Janah:
خَطَّ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي الْأَرْضِ
أَرْبَعَةَ خُطُوطٍ ، قَالَ : تَدْرُونَ مَا هَذَا ؟ فَقَالُوا : اللَّهُ
وَرَسُولُهُ أَعْلَمُ . فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ
وَسَلَّمَ : أَفْضَلُ نِسَاءِ أَهْلِ الْجَنَّةِ : خَدِيجَةُ بِنْتُ
خُوَيْلِدٍ ، وَفَاطِمَةُ بِنْتُ مُحَمَّدٍ ، وَآسِيَةُ بِنْتُ مُزَاحِمٍ
امْرَأَةُ فِرْعَوْنَ ، وَمَرْيَمُ ابْنَةُ عِمْرَانَ رَضِيَ اللَّهُ
Which could be supported by this hadith from Jami' at-Tirmidhi but this narration is without any honorific expression!
So there's no clear consensus about this as it seems, but the expression May Allah be pleased with her would be at least convenient in any case!
And Allah knows best!