I'm not a fan of paying commission on helping for a raise, especially if a shareholder's job. Were it not in your job description, I'd say the same. Founders are ment to build a company, capital is needed to do so. Beyond the expenses you've mentioned, operating cash-flow will be required.
Having said that, I'd turn the conversation to a founder conversation that includes her. You mentioned she has 9%. Who's the CEO? Who are administrators? Group the team together and discuss objectives - not her payout. This can come up later in the talk. Understand that objectives, company needs... these must come before a person's individual desires. Its not just your fiduciary responsibility, but as a team you are required to do the best for the company. You don't want to completely alienate her, if possible, so play into the conversation where, if at all possible, the power of the team can reorganize her thoughts towards the common goal.
Keep this in mind: usually when one person wants money in tight startups, they are thinking one or a few of the following things:
- Their life is hard, they are underpaid, they need money
- They feel that there is a lot of money and the company spare some
- They feel that their value is clearly demonstrated and they can do it all again
Its CRUCIAL that you motivate around common goals and realistic approaches (what do you want to do, how much will it cost) and hopefully get them onboard.
Trust me, you don't want to let the spending go. Not on expenses, not on commissions. GROW the business to sustainability. Cut the shareholder - or risk it - before compromising the good of the company and your objectives.