The vowel sound in the words are different.
The vowel in "aiment" is the same as in "elle". It sounds like the letter M in English or French.
The vowel in "femme" is the same as in the word or letter "a" in French.
lol! Where I'm from "femmes" does NOT rhyme with "bomb" or "Tom", but I can see how it would if you were from upper New York state, for example. In Canada, it might rhyme more with "jam" or "ma'am". ;)