A variety of helmets is difficult, mostly because people try them on then go home and mail order them. You did mention Bell and these folk are close to you.
http://uniongaragenyc.com Mostly they cater to the vintage and scooter crowd with safety in mind. Extremely knowledgeable. folk. You can get her a whole wardrobe there. Tell them Howie from DESMO sent you. The only other place that I can think of with a large selection and reasonable prices is Cycle Therapy
http://www.cycletherapynyc.com can't say I have a warm spot in my heart for them. Oh, don't know what is up with this dealer
http://www.carbonnegative.com formerly Vespa Soho and Mcarran Motors. Vespa Soho had some nice helmets.