I think it was a webtoon (perhapse a manhua/manwa).

It about a strong female lead that got betraid and lost her home and title, as a baron, she later learned from someone she met that she can use magic. During some events (don't remember what), she got transported back in time before she lost it all, but this time she had her magic.

She forms a alians with a mercinary (?), to be able to save her home and keep her title.

Just a little later he swore his sword (I think) to her and she swore her jewle (the heart of a magician) to him. Making them the strongest couple.

Priscilla's Marriage Proposal

~4400 manga completed
~1700 ongoing...

That's the one. Thank you. 😀 😀 😀