Counting the number of letters in a string alphabetically

[TreasureDragon]

This is what I have so far and it is able to print out how many times a letter was printed but in order which it shows up in the string. I want it to first categorize by the number of times it popped up like the example output: (Also mine counts spaces, punctuations, etc. too but I don't want that)

Sentence Statistics :
e appeared 3 times .
a appeared 2 times .
g appeared 2 times .
l appeared 2 times .
o appeared 2 times .

c appeared 1 times .
d appeared 1 times .
i appeared 1 times .
m appeared 1 times .
n appeared 1 times .
t appeared 1 times .
w appeared 1 times .

Yes with the space between >1 and 1.

This is what I have:

string = input("Enter a Sentence: ")

print(f"\nSentence Statistics:")

one = 0

from collections import Counter
count = Counter(string)
for i in string:
    if count[i] == 1 and one == 0:
        print(f"\n{i} appeared {count[i]} times.")
        one += 1
    elif count[i] == 1 and one >= 1:
        print(f"{i} appeared {count[i]} times.")
    if count[i] > 1:
        print(f"{i} appeared {count[i]} times.")

[Yoriz]

from collections import Counter
import string

test_string = 'Sentence Statistics'

counter = Counter(test_string)

for item, count in counter.most_common():
    if item in string.ascii_letters:
        print(f'{item} appeared {count} times')

Output:
t appeared 4 times
e appeared 3 times
S appeared 2 times
n appeared 2 times
c appeared 2 times
i appeared 2 times
s appeared 2 times
a appeared 1 times

[TreasureDragon]

from collections import Counter
import string

test_string = 'Sentence Statistics'

counter = Counter(test_string)

for item, count in counter.most_common():
    if item in string.ascii_letters:
        print(f'{item} appeared {count} times')

Output:
t appeared 4 times
e appeared 3 times
S appeared 2 times
n appeared 2 times
c appeared 2 times
i appeared 2 times
s appeared 2 times
a appeared 1 times

Nice. It's working like a charm. Just how do I alphabetize within the same amount of appearances? Also how do I make it case-insenstitive?
Here's the updated code:

from collections import Counter
import string
 
istring = input("Enter your sentence: ")

counter = Counter(istring)

one = 0

print(f"\nSentence Statistics:")

for item, count in counter.most_common():
    if item in string.ascii_letters:
        if count != 1:
            print(f'{item} appeared {count} times.')
        if count == 1 and one == 0:
            one += 1
            print(f'\n{item} appeared {count} times.')
        elif count == 1 and one != 0:
            print(f'{item} appeared {count} times.')