My baby is 14 months old. I just wanted to tell you that, for me, childbirth and the first year were monumentally hard on my mentally. It was tough enough just to get out of the house or get a shower, let alone pretty yourself up for your man. You are suddenly spending all of your time tending to this little person, and so many of your own needs are completely shoved aside. Of course, you are affected by this new person in your life, too, but I'm just trying to shed some light on her perspective so you can find compassion. (Compassion helps me feel less anger toward my husband, and opens my mind toward solution.)
It is also so tough to get out of those mommy clothes because you need to be in "action-mode." For the first 6 months, I called myself the human burp cloth. I wouldn't dare wear anything nice. And now, after 14 months, at the end of a day of baby-wrangling, changing diapers, and feedings, I really have to make a conscious effort to put myself together for when my husband walks through the door.
One thing that helped me was to buy "mommy clothes" that were not entirely frumpy. They do make these things these days. Check out Victoria's Secret and buy her some cute loungewear as a gift. She'll appreciate the attention, and she just might get the hint.
The way she looks is an outward expression of how she is feeling right now. I bet she feels that her body has taken a toll, she is TIRED from working and being a new mommy, and she does not feel sexy at all. The big t-shirt trap is an easy one to fall into.
Since your baby is only 10 months, and your wife is working and juggling this new role, I can only imagine that she doesn't think a necessary priority at this time of life is to give you some eye candy. So, if you do discuss it with her, please be sure to recognize how well she is doing as a mom. Tell her what you think when you see her holding your baby. If it touches you and makes you feel even closer to her, she should hear it. She can then see that being a mommy doesn't mean that you're all used up and "over".
I would say that you definitely have to help her get in the mindset. In addition to the cute mommy clothes treat, take charge of scheduling the sitter and picking the restaurant or activity. Make it easy on her. Or, how about setting up a spa day for her while you watch the baby. She'll come home feeling great, grateful, and perhaps more in the mood to give of herself to YOU rather than the baby.
I know all of my ideas cost money, so it may or may not be feasible to do all of it. But, you get the idea...
One word of caution: Don't give things or do things expecting immediate sex. It isn't payment for sex. That would not be healthy for your marriage. You are giving of yourself, thinking of her needs, and trying to bring her back to a place of loving you so that she does start to feel like engaging in a sex life with you again.
