I have no problems whatsoever with an affectionate older lady giving advice to a younger one under her care.

What I do not see in the descriptions of Lady Russell's actions, however, is any sign of compromise. Wentworth is wrong for Anne. Wentworth is dangerous. She calls the engagement a 'throwing away' of valuable Anne on the worthless Frederick, and likens it to having Anne snatched off by a stranger, sunk by him so that the new-found hope in Lady Russell's Anne (caused by Capt. Wentworth, although Lady Russell does not acknowledge this) is ground away, leaving her lower than before.

In ch 4:

[Wentworth's confidence] must have been enough for Anne; but Lady Russell saw it very differently.

She is entitled to a different view than Anne, but look at the details of her opinion.

His sanguine temper, and fearlessness of mind, operated very differently on her. She saw in it but an aggravation of the evil. It only added a dangerous character to himself.

Evil? Dangerous? There is no leavening here, no chance that she might be open to her own fallibility.

He was brilliant, he was headstrong. Lady Russell had little taste for wit, and of any thing approaching to imprudence a horror. She deprecated the connexion in every light.

Horror. Deprecated. These are not the words of someone who is listening, or testing to see if they believe their own impressions. She has judged, and is not open to any other interpretation. She does not look to see Anne happier than she has ever been. She does not even say, 'well, let him prove himself, and then get engaged.'