Colin Grove History, item 22.
The "avenue" is almost certainly that entrance to Colin Grove that begins just east of where the brook (the same that passes by Brook House) crosses the Cole Harbour Road. The "gate" mentioned in N9 would seem to mark the entrance to the avenue from the Cole Harbour Road.
In order to afford Louisa a view not only of the avenue but also of the Cole Harbour Road (see reference to "passengers" in O15), her bedroom (which is upstairs--see O22, also S28 and S17) would have to face west or south. Possibly it is at the very southwest corner of the house--with windows looking in both directions. And/or perhaps Louisa's bedroom is the more westward of the two "chambers" bequeathed in 1812 by her grandfather Robert Collins to his youngest daughters Sarah and Susannah as part of their half share of Colin Grove:
"I give Demise and bequeath to my two Daughters Sally Collins and Sukey Collins the South half part of the Farm now Occupied by me with the new Garden and half the Garden South of the House, and the large Meadow the North side of the Main Road fronting the West side of the Dwelling House. Also the North and South front Parlours and East and West (South) Chambers with the Use of the Kitchen and main Pafsage of the said House, and half the Cellar with half the Barn and Out-Houses."Louisa's father was granted the other half of the farm in the same will; he subsequently (in 1813) bought out his sisters for the large sum of 500 pounds. For a more complete excerpt from Robert Collins' will, see Colin Grove History, item 6 .