Why where her friends acting like that do they know he likes her or something

I don't think they know or they're pretending to not know because Miss Pendleton is treated as an old maid and they don't think Mr. Dalton would be that swayed towards her.

in the novel it was described as them wanting miss Pendleton to leave because they were worried she was outshining dora lance, the ball host and their friend

Oh I understand ٩(๑❛ᴗ❛๑)۶

True