Well, then, what’s the point of attributing a miracle to her and putting her on the road to sainthood?
The terminology "attributing a miracle to her" is a bit misleading (although not intentionally so).
The reason the miracle is said to be "attributed" to her is by her intercessory prayer, through her intercessory prayer, her prayer "availeth much" (cf Jas 5:16 this case, God hearing her prayer for the boy and Him choosing to heal him).
From this, .45 Long Colt's question in post 26 is answered, "And why does Rome believe it can determine who is and is not a saint?"
Because in praying for the boy's healing, presumably someone (maybe his parents I don't know it doesn't say) prayed to (asked) Miriam Teresa Demjanovich to pray to God for their son.
Since he was healed, it is concluded God heard Miriam Teresa Demjanovich's prayers for the boy. Since she had passed on when such prayer was requested of her, the only way God would have heard her prayers for the boy was if she were in Heaven, which then makes it safe to conclude she is a Saint (if another miracle is attributed to her intercessory prayer.)