1. Holech rachil megaleh sod, veneman ruach mechaseh davar "He who goes about as a talebearer reveals secrets, but one who is trustworthy in spirit conceals a matter" [Proverbs 11: 13]
2. Goleh sod holech rachil ulfoseh sefasav lo tisarev "He who goes about as a talebearer reveals secrets; do not meddle then with one who sets his lips prating foolishly" [Proverbs 20: 19]
3. If you are told secret, it is forbidden for you to disclose the information even if the information is seemingly benign. Aside from breaching the boundaries of decency and violating the rights of the 'owner of the information'; disclosing classified information can be damaging to the 'owner of the information' as well [Chofetz Chaim: Hilchos Rechilus 5: 7].
4. The prohibition of lashon hara includes spreading damaging information about an individual even if it is not inherently bad [Rambam Hilchos De'os 7: 5].
5. If the ideas were original and creative, Ahuva runs the risk of hijacking Miriam's company's IP which according to the Shoel Umeishiv 1: 44 is included in the biblical prohibition of thievery. [According to Teshuvos Beis Yitzchak, hijacking IP is prohibited because of the law of the land. For more information regarding Halacha and Intellectual Property, see Chasam Sofer Choshen Mishpat 49, 69, 79, Noda Biy'hudah, Choshen Mishpat 2:24, Igros Moshe, Orach Chayim 4:40:19.]
6. If the market can handle it, a local entrepreneur may open a competing establishment [Darchei Moshe 156].
7. Generally, while an employee is under contract with employer A; potential employer B may not convince the employee to consider terminating the contract to change employers.
8. If the employee has unique qualities which are difficult to find; there are those who would permit employer B may attempt to offer him/her incentives to change over. Other's limit this dispensation only to poaching of a Torah teacher  [Choshen Mishpat 237: 2 Sm"a 8, Nesivos 2, See Minchas Pitim].

Exceptions include:

8.1 Darchei Moshe [156] forbids it if doing so will compel the original enterprise to fold .

8.2 If employer A extended extreme effort/investment to obtain this unique employee, employer B may not attempt to convince the employee to switch over to his/her firm [Nachalas Tzvi 237: 2]. [See Nachlas Tzvi when an employee is permitted to do his own investigation to seek more promising opportunities].

Application

Miriam should have used more discretion when discussing her work with Ahuva. If she indeed revealed secrets; aside from breaching possible contractual agreements, she could be guilty of spreading both damaging lashon hara and revealing secrets.

If the secrets were not original, Ahuva is not guilty of stealing Miriam's employer's intellectual property. While there are instances when opening up a competition to a local business is prohibited, generally it is permitted to do so if the market can handle it.

In terms of Ahuva endeavoring to hire Miriam, if Miriam had unique skills/personality and Miriam's initial employer did not invest extreme measures in hiring her, Nesivos would permit Ahuva to approach her even while she was under contract with her initial employer and try to convince her to switch, provided that Ahuva does not severely jeopardize the survival of her competitor's business. Other authorities would only permit the poaching of a Torah teacher under such conditions, but would prohibit poaching employes in any other field of work.