Use a Letter of Intent if: You want to take serious steps towards negotiating the purchase of all or part of a company. You want to secure your interest in a company and request that the sellers exclude negotiating with another buyer.
Also, her closing call to action sounds more like a threat. You want to leave the reader with an avenue for follow-up, but don't intimidate them into responding. After all, they're not obligated to respond. You want to make them want to reach out to you for more information or next steps.