that's correct
Ёж твою двадцать! i don't remember hearing but this could be regional and it sounds completely legit
i heard Ёрш твою меть! Туды ж твою мать!, Етить твою мать! (етить is an archaic synonym of ебать, but today it doesn't sound as obscene as ебать)
there's a variant Едрить твою налево
derivatives Ёшкин кот, Ёкэлэмэнэ, Ёперный театр
here's a list of synonyms
ёб твою мать (ёб твою мать синонимы, синонимы к ёб твою мать)
super creative
the majority of euphemisms to ЁТМ are very folksy and their usage may indicate a member of a certain social group and mostly of an older generation
yeah i agree that's most likely what she heard, an expletive
a phonetic euphemism to бля(дь) is блин
other expletives are сука and на хуй or just на added at the end of a word
there's couple of jokes based on this
- у меня есть дом на
- зачем тебе домна?
- а я в нем живу на
- Алё на ! Это Я на
(Алёна [Helen] and Яна [Joanna]- are feminine names)