to think my dear sister is a bit of a cow?

[RandyRussian]

We used to be really close and chat away on the phone all the time. Nowadays it's less and less and while she expects me to listen to what she has to say as soon as I mention something she ends the call because 'there's someone at the door' or DDs want something' or 'DH has come in' Also she only seems to ring when she wants something. AIBU?

YANBU. As you were previously so close, tell her up front what she'd doing. She may not be aware of it.