Mihalcea began her career in the high jump and reached the peak of the national scene with victories at the Romanian Athletics Championships in 1983 and 1985, competing against Niculina Vasile and Alina Astafei. She achieved a best of in 1985, then had her career best of in 1987, which brought her to thirteenth on the seasonal rankings. Her high jumping career ceased after she was banned for two years by the International Amateur Athletics Federation for testing positive for banned steroids. Following her return from her doping ban, she changed her focus to the pole vault, which was becoming an increasingly popular women's event. She led the way for Romanian women, taking the first three national titles that were available in the sport between 1991 and 1993. She steadily improved to in 1993 then in 1994. She ranked just outside the world's top ten during this period. She cleared four metres for the first time in 1995, doing so both indoors and outdoors. However, she lost her national streak to Gianina Rusu that same year. The 1996 European Athletics Indoor Championships represented the first occasion that a high level international championship had hosted the women's pole vault event. At the competition she achieved a national record height of, taking the bronze medal on countback to Germany's Christine Adams, though both were easily beaten by Icelandic teenager Vala Flosadóttir. The women's pole vault gradually began to be incorporated into major competitions and the standard of the athletes improved. Mihalcea neared four metres in qualifying at the 1997 IAAF World Indoor Championships, but did not make the first ever women's final at the championship. Mihalcea improved her best to that season. The 1998 season saw her become the inaugural champion at the Balkan Indoor Athletics Championships and she also won the 1998 Balkan Athletics Championships title in a championship record of four metres. She returned to the peak of Romanian vaulting in this same period, with national titles in 1998 and 1999. She debuted at the 1998 European Athletics Championships and was among the leading entrants with a new best of. She managed in the first European outdoor final, but this was only enough for fourth as Anzhela Balakhonova, Nicole Humbert and Yvonne Buschbaum shared the podium with equal marks of, which would have been a world record just three years earlier. She achieved her best results in her final year of high level competition in 1999. She was a qualified non-starter at the 1999 IAAF World Indoor Championships, but cleared indoors in Athens to set a meet record at the Balkan Indoor Championships. Mihalcea then followed this with outdoors in Dreux, France. Both of these marks were Romanian national records for the event and were also over-35 masters world records. Her masters marks were bettered by Stacy Dragila in 2008, but she remains the Romanian record holder. Mihalcea had her last marks over four metres in the 2000 season, achieving a best of that season in Gateshead.
