Lady Russell's objection was to a prolonged engagement. That's what Anne and Wentworth were facing until she interfered.

Anne and Captain Wentworth would not have married until Wentworth had earned enough money to support a family (or they'd luckily managed to inherit some from somewhere).

From Chapter 4: Anne Elliot, so young; known to so few, to be snatched off by a stranger without alliance or fortune; or rather sunk by him into a state of most wearing, anxious, youth-killing dependance!

Notice in this line how Lady Russell starts off by talking about marriage ("to be snatched off") and then corrects herself ("or rather"), Anne will be stuck at Kellynch for an indefinite period of time, worrying about him as he's off earning the fortune for them to marry on.

Furthermore all the words in this chapter are about engagement She [Anne]was persuaded ... she should yet have been a happier woman in maintaining the engagement ... .