Umm, what do you want to do with it? There are only two places in USPSA where a 9mm of any stripe can compete with a .40 or larger. One is in production class where everything is scored at minor power factor. All guns used must be DA first shot or Glock types. 10 rd mags, quite possibly the cheapest class to get into.
The other is in Open class. A recent rule change now allows making major power factor with 9x19. The people that are going that way I assume are doing so based on brass cost. There are still plenty of .38 supers, TJs, Super-comps, 9x23 etc. Anything larger diameter in Open class is a capacity handicap. making major with 9mm is not something for the novice reloader. A 115gr bullet at 1450, a 124gr at 1350, or a 147gr at 1130 is some basic numbers. That is screaming for a case of such limited capacity.
Any shooting done with a 9mm 1911 will leave you at a disadvantage. You can't make major with it in Limited or Limited 10. (.40 cal min. for major) Since it is a Single action you can't run it in production. If she wants a 1911 for IPSC make it .40 or .45 and run it in Limited 10. If she wants a high dollar 1911 get her a double stack STI and shoot limited. If you get her an open gun it can be 9mm, but won't exactly be suitable for IDPA.
On the other hand a 10rd 9mm 1911 is just about a perfect gun for IDPA. So, it's obvios, buy her two 1911s.
Your local expert is projecting his prejudice onto your wife. The "little woman" can handle a .45 just fine unless there is a physical disability. In fact I have had a few women of about that size shoot circles around me with large bore 1911s. Get her what she likes best.