Sorry, I didn't mean to discourage you. It's just that you said you're hoping to get some HM's which are IMO quite recessive against round tail. I only wanted you to understand what you're up against. You could keep crossing the offspring to new HM's .... but this means constantly buying new bettas.
If you spawn her to an extended red, you may get multi blue, red with irids, cambodian like colors with irids, cellophane/pastel like colors, plus a number of possibilities depending on their genetic background.
If it's a cherry red, you should only get blue and red multi (blue with red or red with irid). Some may turn out more solid looking than others, plus the hidden genetic background.