I plan to breed my Froslass but in the chance I get a female can I evolve it into a Glalie will it still evolve into a Froslass like a 3 evolution chain or will it stay a female Glalie forever?
Glalie evolves from Snorunt starting at level 42. It is one of Snorunt's final forms, the other being Froslass.
A female Snorunt will evolve from Snorunt by normal level up. Frosslass will only evolve from Snorunt via exposure to a Dawn Stone on a female Snorunt.
So your Snorunt offspring (from breeding your Frosslass) will be able to evolve into a Glalie or Froslass. When it has evolved into a Glalie it cannot evolve into a Froslass - they are alternative evolutions, and not part of a linear evolution chain.
Glalie (Bulpabedpia)
It will stay female glalie forever. It's like the slowbro/ slowking evolutions.
Source: experience