Formula milk

Hi parents.. my little princess is 3 months now. Fully BF. I’ll be going to work next week. I have stored expressed BM in the freezer & will only last for 3-5 days. I’ll be pumping at work see how’s the situation and etc. Worry that my milk will not enough for her hence tot of mixing formula milk if needed. To practice bought frisolac comfort. Gave frisolac comfort 2oz at 10pm, EBM prepared and wanted to feed her at 1am. Before feeding she vomited all the milk which was last feeding - frisolac. Therefore, she don’t frisolac or should I try to give her once more? Please advice . She only accept DF before as she don’t accept Any bottle feeding. After few trials, she like medela bottle feeding and continue to giver her via bottle (EBM) A’s wanna practice her to use bottle. Since I’ll be going work. Pls advice regards to formula milk .. thank u in advance